<?xml version="1.0" encoding="UTF-8"?>

<!--XBRL Document Created with Wdesk from Workiva-->
<!--Copyright 2020 Workiva-->
<!--r:d3440bbe-9fbb-4888-8b82-2432f35bffd6,g:d31c1c56-ea31-42ac-8622-79fee594d81f-->
<link:linkbase xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member"/>
  <link:roleRef roleURI="http://www.gentex.com/role/CoverPage" xlink:type="simple" xlink:href="gntx-20200630.xsd#CoverPage"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/CoverPage" xlink:type="extended" id="i0e1b553de04a48b0985e0691781c4b64_CoverPage"/>
  <link:roleRef roleURI="http://www.gentex.com/role/UnauditedCondensedConsolidatedBalanceSheets" xlink:type="simple" xlink:href="gntx-20200630.xsd#UnauditedCondensedConsolidatedBalanceSheets"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/UnauditedCondensedConsolidatedBalanceSheets" xlink:type="extended" id="i2e6be8bfdd7e4b4da1b4bc52acd3331e_UnauditedCondensedConsolidatedBalanceSheets"/>
  <link:roleRef roleURI="http://www.gentex.com/role/UnauditedCondensedConsolidatedStatementsofIncome" xlink:type="simple" xlink:href="gntx-20200630.xsd#UnauditedCondensedConsolidatedStatementsofIncome"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/UnauditedCondensedConsolidatedStatementsofIncome" xlink:type="extended" id="ia667aade4f8142e8b86ca7d01b7b4172_UnauditedCondensedConsolidatedStatementsofIncome"/>
  <link:roleRef roleURI="http://www.gentex.com/role/UnauditedCondensedConsolidatedStatementsofComprehensiveIncome" xlink:type="simple" xlink:href="gntx-20200630.xsd#UnauditedCondensedConsolidatedStatementsofComprehensiveIncome"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/UnauditedCondensedConsolidatedStatementsofComprehensiveIncome" xlink:type="extended" id="i33d6b4d273974fdeac6b90a4ade9b4a8_UnauditedCondensedConsolidatedStatementsofComprehensiveIncome"/>
  <link:roleRef roleURI="http://www.gentex.com/role/UnauditedCondensedConsolidatedStatementsofShareholdersInvestment" xlink:type="simple" xlink:href="gntx-20200630.xsd#UnauditedCondensedConsolidatedStatementsofShareholdersInvestment"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/UnauditedCondensedConsolidatedStatementsofShareholdersInvestment" xlink:type="extended" id="ic5388a245cd6454fbd52c95930da32cd_UnauditedCondensedConsolidatedStatementsofShareholdersInvestment">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_e7bf9fd8-fb32-46ba-9adf-0733591ad2c4" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_f22192d5-71a7-4051-a90f-3fd7ce367e13" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_e7bf9fd8-fb32-46ba-9adf-0733591ad2c4" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_f22192d5-71a7-4051-a90f-3fd7ce367e13" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_d6e620d2-84b0-40ba-9347-2bfd2b889b7c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_f22192d5-71a7-4051-a90f-3fd7ce367e13" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_d6e620d2-84b0-40ba-9347-2bfd2b889b7c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_736a1d8a-51a2-4e21-885a-a347ee56d47c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_f22192d5-71a7-4051-a90f-3fd7ce367e13" xlink:to="loc_us-gaap_StockholdersEquity_736a1d8a-51a2-4e21-885a-a347ee56d47c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_6d2da783-a22a-4443-a5b9-96a65a6937e8" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesNewIssues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_f22192d5-71a7-4051-a90f-3fd7ce367e13" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_6d2da783-a22a-4443-a5b9-96a65a6937e8" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueNewIssues_a68178ba-faee-4d00-9719-df7600738544" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockIssuedDuringPeriodValueNewIssues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_f22192d5-71a7-4051-a90f-3fd7ce367e13" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueNewIssues_a68178ba-faee-4d00-9719-df7600738544" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesAcquisitions_52bd9da9-5bfb-48f2-9400-0c2888661211" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesAcquisitions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_f22192d5-71a7-4051-a90f-3fd7ce367e13" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesAcquisitions_52bd9da9-5bfb-48f2-9400-0c2888661211" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueAcquisitions_5d9e807e-9082-4c6b-a368-ec1e2b8808fc" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockIssuedDuringPeriodValueAcquisitions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_f22192d5-71a7-4051-a90f-3fd7ce367e13" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueAcquisitions_5d9e807e-9082-4c6b-a368-ec1e2b8808fc" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchasedDuringPeriodShares_e2b74f95-9bac-4aed-9e2c-32b09a15e5f6" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockRepurchasedDuringPeriodShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_f22192d5-71a7-4051-a90f-3fd7ce367e13" xlink:to="loc_us-gaap_StockRepurchasedDuringPeriodShares_e2b74f95-9bac-4aed-9e2c-32b09a15e5f6" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchasedDuringPeriodValue_79303057-a8ff-44f5-9627-ef3bcde63143" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockRepurchasedDuringPeriodValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_f22192d5-71a7-4051-a90f-3fd7ce367e13" xlink:to="loc_us-gaap_StockRepurchasedDuringPeriodValue_79303057-a8ff-44f5-9627-ef3bcde63143" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_57e6ce06-5d45-4255-9ce0-e268b5e7e3c6" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_f22192d5-71a7-4051-a90f-3fd7ce367e13" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_57e6ce06-5d45-4255-9ce0-e268b5e7e3c6" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DividendsCommonStockCash_bf579dc9-86ab-4302-b108-98c1cff91556" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DividendsCommonStockCash"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_f22192d5-71a7-4051-a90f-3fd7ce367e13" xlink:to="loc_us-gaap_DividendsCommonStockCash_bf579dc9-86ab-4302-b108-98c1cff91556" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_31b0be75-86f5-4131-b0f0-4ac40c44df42" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_f22192d5-71a7-4051-a90f-3fd7ce367e13" xlink:to="loc_us-gaap_NetIncomeLoss_31b0be75-86f5-4131-b0f0-4ac40c44df42" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_4877db6e-a860-479f-839c-46214b5dea2b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_f22192d5-71a7-4051-a90f-3fd7ce367e13" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_4877db6e-a860-479f-839c-46214b5dea2b" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_a73cdc31-3355-4bb6-8c22-bc86554ce7de" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_d1a3cce3-6005-4391-858e-7aa540707d95" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockholdersEquity"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_72fc6811-da05-466b-9515-3d8e86ba06cd" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_e7bf9fd8-fb32-46ba-9adf-0733591ad2c4" xlink:to="loc_us-gaap_StatementTable_72fc6811-da05-466b-9515-3d8e86ba06cd" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_f443330e-ca64-47db-8d61-e09a8d6fa650" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_72fc6811-da05-466b-9515-3d8e86ba06cd" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_f443330e-ca64-47db-8d61-e09a8d6fa650" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_f443330e-ca64-47db-8d61-e09a8d6fa650_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_f443330e-ca64-47db-8d61-e09a8d6fa650" xlink:to="loc_us-gaap_EquityComponentDomain_f443330e-ca64-47db-8d61-e09a8d6fa650_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_81aa998b-efa6-4953-9958-a28f897f8b8e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_f443330e-ca64-47db-8d61-e09a8d6fa650" xlink:to="loc_us-gaap_EquityComponentDomain_81aa998b-efa6-4953-9958-a28f897f8b8e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_9085747e-828b-43d6-b906-112ef40a9b45" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_81aa998b-efa6-4953-9958-a28f897f8b8e" xlink:to="loc_us-gaap_CommonStockMember_9085747e-828b-43d6-b906-112ef40a9b45" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_0d4fe664-bf2f-4b8b-bec2-1ac8359da7b6" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AdditionalPaidInCapitalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_81aa998b-efa6-4953-9958-a28f897f8b8e" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_0d4fe664-bf2f-4b8b-bec2-1ac8359da7b6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_363577d8-def6-4dff-b832-2e59ada16cf7" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RetainedEarningsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_81aa998b-efa6-4953-9958-a28f897f8b8e" xlink:to="loc_us-gaap_RetainedEarningsMember_363577d8-def6-4dff-b832-2e59ada16cf7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_6c1c94e9-f323-490d-a113-71a73b463078" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_81aa998b-efa6-4953-9958-a28f897f8b8e" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_6c1c94e9-f323-490d-a113-71a73b463078" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.gentex.com/role/UnauditedCondensedConsolidatedStatementsofShareholdersInvestmentParenthetical" xlink:type="simple" xlink:href="gntx-20200630.xsd#UnauditedCondensedConsolidatedStatementsofShareholdersInvestmentParenthetical"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/UnauditedCondensedConsolidatedStatementsofShareholdersInvestmentParenthetical" xlink:type="extended" id="i4968974769d24b139d668d8e6cb834ee_UnauditedCondensedConsolidatedStatementsofShareholdersInvestmentParenthetical"/>
  <link:roleRef roleURI="http://www.gentex.com/role/UnauditedCondensedConsolidatedStatementsofCashFlows" xlink:type="simple" xlink:href="gntx-20200630.xsd#UnauditedCondensedConsolidatedStatementsofCashFlows"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/UnauditedCondensedConsolidatedStatementsofCashFlows" xlink:type="extended" id="ie82bb49410bb4ffc89444eb7f2ccb2e5_UnauditedCondensedConsolidatedStatementsofCashFlows"/>
  <link:roleRef roleURI="http://www.gentex.com/role/BasisofPresentation" xlink:type="simple" xlink:href="gntx-20200630.xsd#BasisofPresentation"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/BasisofPresentation" xlink:type="extended" id="ib33f92f9b96a4a88b0ff165cd70f2398_BasisofPresentation"/>
  <link:roleRef roleURI="http://www.gentex.com/role/AdoptionofNewAccountingPronouncements" xlink:type="simple" xlink:href="gntx-20200630.xsd#AdoptionofNewAccountingPronouncements"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/AdoptionofNewAccountingPronouncements" xlink:type="extended" id="iecbb1b51c52f4977b2d679625d3d035a_AdoptionofNewAccountingPronouncements"/>
  <link:roleRef roleURI="http://www.gentex.com/role/AdoptionofNewAccountingPronouncementsPolicies" xlink:type="simple" xlink:href="gntx-20200630.xsd#AdoptionofNewAccountingPronouncementsPolicies"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/AdoptionofNewAccountingPronouncementsPolicies" xlink:type="extended" id="ie7366a8f5f3e49a29765aeadfe154f42_AdoptionofNewAccountingPronouncementsPolicies"/>
  <link:roleRef roleURI="http://www.gentex.com/role/GoodwillandOtherIntangibleAssets" xlink:type="simple" xlink:href="gntx-20200630.xsd#GoodwillandOtherIntangibleAssets"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/GoodwillandOtherIntangibleAssets" xlink:type="extended" id="ia7a57b90f56e4b8583ee07bb7ef81493_GoodwillandOtherIntangibleAssets"/>
  <link:roleRef roleURI="http://www.gentex.com/role/GoodwillandOtherIntangibleAssetsTables" xlink:type="simple" xlink:href="gntx-20200630.xsd#GoodwillandOtherIntangibleAssetsTables"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/GoodwillandOtherIntangibleAssetsTables" xlink:type="extended" id="i872f145567274a00b423fccd4618712f_GoodwillandOtherIntangibleAssetsTables"/>
  <link:roleRef roleURI="http://www.gentex.com/role/GoodwillandOtherIntangibleAssetsNarrativeDetails" xlink:type="simple" xlink:href="gntx-20200630.xsd#GoodwillandOtherIntangibleAssetsNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/GoodwillandOtherIntangibleAssetsNarrativeDetails" xlink:type="extended" id="idb3fdb11c2cf41e89299e4ee75b62be4_GoodwillandOtherIntangibleAssetsNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_c359e012-8784-48e2-8b6a-c2f23c754059" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_bbe36aee-a023-4334-a318-632842b8903d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_Goodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_c359e012-8784-48e2-8b6a-c2f23c754059" xlink:to="loc_us-gaap_Goodwill_bbe36aee-a023-4334-a318-632842b8903d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillAcquiredDuringPeriod_57baa97b-9d8a-49e5-ba77-b35e0856ee20" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_GoodwillAcquiredDuringPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_c359e012-8784-48e2-8b6a-c2f23c754059" xlink:to="loc_us-gaap_GoodwillAcquiredDuringPeriod_57baa97b-9d8a-49e5-ba77-b35e0856ee20" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationOfIntangibleAssets_0a17a70d-d3a7-42fb-b9a1-16f3b5e9e3c0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AmortizationOfIntangibleAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_c359e012-8784-48e2-8b6a-c2f23c754059" xlink:to="loc_us-gaap_AmortizationOfIntangibleAssets_0a17a70d-d3a7-42fb-b9a1-16f3b5e9e3c0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseRemainderOfFiscalYear_1644010d-7e9e-49db-a0c8-ecbded1d7a67" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseRemainderOfFiscalYear"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_c359e012-8784-48e2-8b6a-c2f23c754059" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseRemainderOfFiscalYear_1644010d-7e9e-49db-a0c8-ecbded1d7a67" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths_12be11cf-8d71-4a62-b50b-d7d72b5edbe9" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_c359e012-8784-48e2-8b6a-c2f23c754059" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths_12be11cf-8d71-4a62-b50b-d7d72b5edbe9" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo_12fc8b44-c518-4ed1-8cfe-b33f447530c5" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_c359e012-8784-48e2-8b6a-c2f23c754059" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo_12fc8b44-c518-4ed1-8cfe-b33f447530c5" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearThree_0d83348c-b630-4692-aed9-2d18258eab54" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearThree"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_c359e012-8784-48e2-8b6a-c2f23c754059" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearThree_0d83348c-b630-4692-aed9-2d18258eab54" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFour_9d79856e-fbf8-48ee-8d39-879709260c3f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFour"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_c359e012-8784-48e2-8b6a-c2f23c754059" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFour_9d79856e-fbf8-48ee-8d39-879709260c3f" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_aa364e60-5115-4191-8370-eaf74a3a3286" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_c359e012-8784-48e2-8b6a-c2f23c754059" xlink:to="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_aa364e60-5115-4191-8370-eaf74a3a3286" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_a2536faf-0252-48aa-9a21-fbf78be22988" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_aa364e60-5115-4191-8370-eaf74a3a3286" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_a2536faf-0252-48aa-9a21-fbf78be22988" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_a2536faf-0252-48aa-9a21-fbf78be22988_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_a2536faf-0252-48aa-9a21-fbf78be22988" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_a2536faf-0252-48aa-9a21-fbf78be22988_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_9194c390-6cc2-45c9-ad2c-77170fc373c5" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_a2536faf-0252-48aa-9a21-fbf78be22988" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_9194c390-6cc2-45c9-ad2c-77170fc373c5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_HomeLinkMember_c399c07e-6308-4ec4-80b5-141350f9a14b" xlink:href="gntx-20200630.xsd#gntx_HomeLinkMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_9194c390-6cc2-45c9-ad2c-77170fc373c5" xlink:to="loc_gntx_HomeLinkMember_c399c07e-6308-4ec4-80b5-141350f9a14b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_VaporsensIncMember_81f55200-79d5-4213-a07d-fc5b035b08f3" xlink:href="gntx-20200630.xsd#gntx_VaporsensIncMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_9194c390-6cc2-45c9-ad2c-77170fc373c5" xlink:to="loc_gntx_VaporsensIncMember_81f55200-79d5-4213-a07d-fc5b035b08f3" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.gentex.com/role/GoodwillandOtherIntangibleAssetsScheduleofGoodwillDetails" xlink:type="simple" xlink:href="gntx-20200630.xsd#GoodwillandOtherIntangibleAssetsScheduleofGoodwillDetails"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/GoodwillandOtherIntangibleAssetsScheduleofGoodwillDetails" xlink:type="extended" id="idf3b0f2fdddc417eacac53711891f148_GoodwillandOtherIntangibleAssetsScheduleofGoodwillDetails"/>
  <link:roleRef roleURI="http://www.gentex.com/role/GoodwillandOtherIntangibleAssetsScheduleofIntangibleAssetsDetails" xlink:type="simple" xlink:href="gntx-20200630.xsd#GoodwillandOtherIntangibleAssetsScheduleofIntangibleAssetsDetails"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/GoodwillandOtherIntangibleAssetsScheduleofIntangibleAssetsDetails" xlink:type="extended" id="i1b1ad331eb7d48ed96da447f967dc9aa_GoodwillandOtherIntangibleAssetsScheduleofIntangibleAssetsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_3cd5c682-5c91-4b3d-b7af-3c32c1dd2cad" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsGross_8c852c3f-2a95-41ad-8672-83ec8d8027d5" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_3cd5c682-5c91-4b3d-b7af-3c32c1dd2cad" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsGross_8c852c3f-2a95-41ad-8672-83ec8d8027d5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_ac0a6750-40ed-48fe-874b-552916b99fa0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_3cd5c682-5c91-4b3d-b7af-3c32c1dd2cad" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_ac0a6750-40ed-48fe-874b-552916b99fa0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsNet_973f6703-6f43-404b-9c2a-021abdaa3ac5" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_3cd5c682-5c91-4b3d-b7af-3c32c1dd2cad" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsNet_973f6703-6f43-404b-9c2a-021abdaa3ac5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill_6b9e3d3a-aa3f-4f0c-87e5-1800435fa563" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_3cd5c682-5c91-4b3d-b7af-3c32c1dd2cad" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill_6b9e3d3a-aa3f-4f0c-87e5-1800435fa563" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IntangibleAssetsGrossExcludingGoodwill_4cdad46b-351d-454b-a8b2-2f17ebfe83fc" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IntangibleAssetsGrossExcludingGoodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_3cd5c682-5c91-4b3d-b7af-3c32c1dd2cad" xlink:to="loc_us-gaap_IntangibleAssetsGrossExcludingGoodwill_4cdad46b-351d-454b-a8b2-2f17ebfe83fc" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_08e7fb1f-64c4-4553-8ca5-88362e1b5826" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IntangibleAssetsNetExcludingGoodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_3cd5c682-5c91-4b3d-b7af-3c32c1dd2cad" xlink:to="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_08e7fb1f-64c4-4553-8ca5-88362e1b5826" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetUsefulLife_a154e9f7-9195-462a-a43b-5c8eeab8ee0d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetUsefulLife"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_3cd5c682-5c91-4b3d-b7af-3c32c1dd2cad" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetUsefulLife_a154e9f7-9195-462a-a43b-5c8eeab8ee0d" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_1169dab3-09c2-4294-b85e-52de3e3dd0e4" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_3cd5c682-5c91-4b3d-b7af-3c32c1dd2cad" xlink:to="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_1169dab3-09c2-4294-b85e-52de3e3dd0e4" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_3fc20dea-d1ad-48ad-96d6-66c3edfb7959" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_1169dab3-09c2-4294-b85e-52de3e3dd0e4" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_3fc20dea-d1ad-48ad-96d6-66c3edfb7959" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_3fc20dea-d1ad-48ad-96d6-66c3edfb7959_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_3fc20dea-d1ad-48ad-96d6-66c3edfb7959" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_3fc20dea-d1ad-48ad-96d6-66c3edfb7959_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_7d173007-5db0-4e7f-a1d5-4394b65eb005" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis_3fc20dea-d1ad-48ad-96d6-66c3edfb7959" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_7d173007-5db0-4e7f-a1d5-4394b65eb005" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TrademarksAndTradeNamesMember_199634c7-f6d0-4804-851f-13e1fbd15b10" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TrademarksAndTradeNamesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_7d173007-5db0-4e7f-a1d5-4394b65eb005" xlink:to="loc_us-gaap_TrademarksAndTradeNamesMember_199634c7-f6d0-4804-851f-13e1fbd15b10" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LicensingAgreementsMember_46ed0273-0c24-4d01-997d-cb226b51c2ec" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LicensingAgreementsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_7d173007-5db0-4e7f-a1d5-4394b65eb005" xlink:to="loc_us-gaap_LicensingAgreementsMember_46ed0273-0c24-4d01-997d-cb226b51c2ec" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InProcessResearchAndDevelopmentMember_f975ec4a-c4f0-4219-87aa-05f7e58fd4fa" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InProcessResearchAndDevelopmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IndefiniteLivedIntangibleAssetsMajorClassNameDomain_7d173007-5db0-4e7f-a1d5-4394b65eb005" xlink:to="loc_us-gaap_InProcessResearchAndDevelopmentMember_f975ec4a-c4f0-4219-87aa-05f7e58fd4fa" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_38bed120-01cd-4dbb-aed3-3ff757b085a1" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_1169dab3-09c2-4294-b85e-52de3e3dd0e4" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_38bed120-01cd-4dbb-aed3-3ff757b085a1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_38bed120-01cd-4dbb-aed3-3ff757b085a1_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_38bed120-01cd-4dbb-aed3-3ff757b085a1" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_38bed120-01cd-4dbb-aed3-3ff757b085a1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_52a5a5d8-ed1b-43ed-844c-eedeb84f504f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_38bed120-01cd-4dbb-aed3-3ff757b085a1" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_52a5a5d8-ed1b-43ed-844c-eedeb84f504f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PatentsMember_61889d16-315d-404b-b92a-51467ae8dd34" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PatentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_52a5a5d8-ed1b-43ed-844c-eedeb84f504f" xlink:to="loc_us-gaap_PatentsMember_61889d16-315d-404b-b92a-51467ae8dd34" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TechnologyBasedIntangibleAssetsMember_9dbc0a67-9768-467c-8000-31de9ef1f399" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TechnologyBasedIntangibleAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_52a5a5d8-ed1b-43ed-844c-eedeb84f504f" xlink:to="loc_us-gaap_TechnologyBasedIntangibleAssetsMember_9dbc0a67-9768-467c-8000-31de9ef1f399" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DevelopedTechnologyRightsMember_77cfb79d-b662-4a7d-83c9-d0602258bd8e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DevelopedTechnologyRightsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_52a5a5d8-ed1b-43ed-844c-eedeb84f504f" xlink:to="loc_us-gaap_DevelopedTechnologyRightsMember_77cfb79d-b662-4a7d-83c9-d0602258bd8e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerContractsMember_1edcc470-7e12-4dc0-8592-161dcb5f2007" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CustomerContractsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_52a5a5d8-ed1b-43ed-844c-eedeb84f504f" xlink:to="loc_us-gaap_CustomerContractsMember_1edcc470-7e12-4dc0-8592-161dcb5f2007" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_PatentsandOtherIntangibleAssetsMember_c5d4d1f2-1958-4003-8f7a-4f92dcd61767" xlink:href="gntx-20200630.xsd#gntx_PatentsandOtherIntangibleAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_52a5a5d8-ed1b-43ed-844c-eedeb84f504f" xlink:to="loc_gntx_PatentsandOtherIntangibleAssetsMember_c5d4d1f2-1958-4003-8f7a-4f92dcd61767" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.gentex.com/role/Investments" xlink:type="simple" xlink:href="gntx-20200630.xsd#Investments"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/Investments" xlink:type="extended" id="i080bfaa2873f43ea813990bfec627395_Investments"/>
  <link:roleRef roleURI="http://www.gentex.com/role/InvestmentsTables" xlink:type="simple" xlink:href="gntx-20200630.xsd#InvestmentsTables"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/InvestmentsTables" xlink:type="extended" id="ifd4567ce0efe4737922f04896dc15674_InvestmentsTables"/>
  <link:roleRef roleURI="http://www.gentex.com/role/InvestmentsNarrativeDetails" xlink:type="simple" xlink:href="gntx-20200630.xsd#InvestmentsNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/InvestmentsNarrativeDetails" xlink:type="extended" id="ieb6c106daf044c07bd10a9248f8e2e11_InvestmentsNarrativeDetails"/>
  <link:roleRef roleURI="http://www.gentex.com/role/InvestmentsScheduleofAssetsorLiabilitiesRecurringFairValueMeasurementsDetails" xlink:type="simple" xlink:href="gntx-20200630.xsd#InvestmentsScheduleofAssetsorLiabilitiesRecurringFairValueMeasurementsDetails"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/InvestmentsScheduleofAssetsorLiabilitiesRecurringFairValueMeasurementsDetails" xlink:type="extended" id="i5b40f695151e429797af00577f9ba240_InvestmentsScheduleofAssetsorLiabilitiesRecurringFairValueMeasurementsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_804b6b38-219f-41dc-a590-9d884a0334b1" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_a701bdea-e915-4581-abc4-366a6cd2e7c2" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CashAndCashEquivalentsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_804b6b38-219f-41dc-a590-9d884a0334b1" xlink:to="loc_us-gaap_CashAndCashEquivalentsFairValueDisclosure_a701bdea-e915-4581-abc4-366a6cd2e7c2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentsFairValueDisclosure_a292c9c5-5e99-48a5-bb1b-6d7faced059f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InvestmentsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_804b6b38-219f-41dc-a590-9d884a0334b1" xlink:to="loc_us-gaap_InvestmentsFairValueDisclosure_a292c9c5-5e99-48a5-bb1b-6d7faced059f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentsAndCash_369f475a-ca6b-4e7a-afb3-2338a0a3a2cd" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InvestmentsAndCash"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_804b6b38-219f-41dc-a590-9d884a0334b1" xlink:to="loc_us-gaap_InvestmentsAndCash_369f475a-ca6b-4e7a-afb3-2338a0a3a2cd" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_c7330dd8-1c09-4a8e-88a6-ee3de5514695" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_804b6b38-219f-41dc-a590-9d884a0334b1" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_c7330dd8-1c09-4a8e-88a6-ee3de5514695" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeAxis_0d30db8b-7e89-4e26-8a9f-2a2f493090b5" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InvestmentTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_c7330dd8-1c09-4a8e-88a6-ee3de5514695" xlink:to="loc_us-gaap_InvestmentTypeAxis_0d30db8b-7e89-4e26-8a9f-2a2f493090b5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeCategorizationMember_0d30db8b-7e89-4e26-8a9f-2a2f493090b5_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InvestmentTypeCategorizationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_InvestmentTypeAxis_0d30db8b-7e89-4e26-8a9f-2a2f493090b5" xlink:to="loc_us-gaap_InvestmentTypeCategorizationMember_0d30db8b-7e89-4e26-8a9f-2a2f493090b5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeCategorizationMember_68709ff4-129a-42a9-a060-9496e6c71c93" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InvestmentTypeCategorizationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_InvestmentTypeAxis_0d30db8b-7e89-4e26-8a9f-2a2f493090b5" xlink:to="loc_us-gaap_InvestmentTypeCategorizationMember_68709ff4-129a-42a9-a060-9496e6c71c93" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermInvestmentsMember_599c44d7-c17f-4a05-809a-fa59045ca27d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShortTermInvestmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_68709ff4-129a-42a9-a060-9496e6c71c93" xlink:to="loc_us-gaap_ShortTermInvestmentsMember_599c44d7-c17f-4a05-809a-fa59045ca27d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLongTermInvestmentsMember_402fef3f-5254-4a1b-a69b-cbdb0f816b06" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherLongTermInvestmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_68709ff4-129a-42a9-a060-9496e6c71c93" xlink:to="loc_us-gaap_OtherLongTermInvestmentsMember_402fef3f-5254-4a1b-a69b-cbdb0f816b06" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_86923b42-193e-4501-895c-a2f3c81d615c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_c7330dd8-1c09-4a8e-88a6-ee3de5514695" xlink:to="loc_us-gaap_FinancialInstrumentAxis_86923b42-193e-4501-895c-a2f3c81d615c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_86923b42-193e-4501-895c-a2f3c81d615c_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_86923b42-193e-4501-895c-a2f3c81d615c" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_86923b42-193e-4501-895c-a2f3c81d615c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_f3e49ce1-ff3e-4d6d-ae47-8e63c3b801b2" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_86923b42-193e-4501-895c-a2f3c81d615c" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_f3e49ce1-ff3e-4d6d-ae47-8e63c3b801b2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CertificatesOfDepositMember_66403646-41a4-4a76-9664-75671cba940d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CertificatesOfDepositMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_f3e49ce1-ff3e-4d6d-ae47-8e63c3b801b2" xlink:to="loc_us-gaap_CertificatesOfDepositMember_66403646-41a4-4a76-9664-75671cba940d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateBondSecuritiesMember_b2fe9063-35e8-4a38-b4bb-58aa40036a26" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CorporateBondSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_f3e49ce1-ff3e-4d6d-ae47-8e63c3b801b2" xlink:to="loc_us-gaap_CorporateBondSecuritiesMember_b2fe9063-35e8-4a38-b4bb-58aa40036a26" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USTreasurySecuritiesMember_81c6fe28-268d-42f7-b3ae-9bb8a68f73f9" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_USTreasurySecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_f3e49ce1-ff3e-4d6d-ae47-8e63c3b801b2" xlink:to="loc_us-gaap_USTreasurySecuritiesMember_81c6fe28-268d-42f7-b3ae-9bb8a68f73f9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MunicipalBondsMember_18509c04-a291-4e5b-a29f-1849d5cf176a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_MunicipalBondsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_f3e49ce1-ff3e-4d6d-ae47-8e63c3b801b2" xlink:to="loc_us-gaap_MunicipalBondsMember_18509c04-a291-4e5b-a29f-1849d5cf176a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherDebtSecuritiesMember_63c0cde7-7b11-4d6b-86be-2c5d7900d439" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_f3e49ce1-ff3e-4d6d-ae47-8e63c3b801b2" xlink:to="loc_us-gaap_OtherDebtSecuritiesMember_63c0cde7-7b11-4d6b-86be-2c5d7900d439" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetBackedSecuritiesMember_7ddbe45a-5d6b-4f67-9323-69485379d988" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AssetBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_f3e49ce1-ff3e-4d6d-ae47-8e63c3b801b2" xlink:to="loc_us-gaap_AssetBackedSecuritiesMember_7ddbe45a-5d6b-4f67-9323-69485379d988" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_8e4a3dcd-cc92-42a9-9f5a-e6eb1ea0f56d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_c7330dd8-1c09-4a8e-88a6-ee3de5514695" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_8e4a3dcd-cc92-42a9-9f5a-e6eb1ea0f56d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_8e4a3dcd-cc92-42a9-9f5a-e6eb1ea0f56d_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_8e4a3dcd-cc92-42a9-9f5a-e6eb1ea0f56d" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_8e4a3dcd-cc92-42a9-9f5a-e6eb1ea0f56d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_48ae7872-edf4-44ab-9b92-710b8b2e1c9e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_8e4a3dcd-cc92-42a9-9f5a-e6eb1ea0f56d" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_48ae7872-edf4-44ab-9b92-710b8b2e1c9e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_0553257f-d976-4f20-bf76-0fa72dd20617" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueInputsLevel1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_48ae7872-edf4-44ab-9b92-710b8b2e1c9e" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_0553257f-d976-4f20-bf76-0fa72dd20617" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_33911ec3-c86e-4989-bc48-2c35fe1ef928" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_48ae7872-edf4-44ab-9b92-710b8b2e1c9e" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_33911ec3-c86e-4989-bc48-2c35fe1ef928" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_1048293e-a827-44c1-a6f3-8adce9915855" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FairValueInputsLevel3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_48ae7872-edf4-44ab-9b92-710b8b2e1c9e" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_1048293e-a827-44c1-a6f3-8adce9915855" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.gentex.com/role/InvestmentsScheduleofAmortizedCostUnrealizedGainsandLossesandMarketValueofInvestmentSecuritiesDetails" xlink:type="simple" xlink:href="gntx-20200630.xsd#InvestmentsScheduleofAmortizedCostUnrealizedGainsandLossesandMarketValueofInvestmentSecuritiesDetails"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/InvestmentsScheduleofAmortizedCostUnrealizedGainsandLossesandMarketValueofInvestmentSecuritiesDetails" xlink:type="extended" id="i6200a52a78a04771888b703b9ff470d1_InvestmentsScheduleofAmortizedCostUnrealizedGainsandLossesandMarketValueofInvestmentSecuritiesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_d8cc33f7-bc13-4b39-b707-5a1951a5a22c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleAmortizedCostCurrent_3a74d98f-602d-4d65-bbe8-5f86ae925757" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtSecuritiesAvailableForSaleAmortizedCostCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_d8cc33f7-bc13-4b39-b707-5a1951a5a22c" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleAmortizedCostCurrent_3a74d98f-602d-4d65-bbe8-5f86ae925757" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_1d70973e-c38b-41cc-b3dd-bb5349d6cd0f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_d8cc33f7-bc13-4b39-b707-5a1951a5a22c" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_1d70973e-c38b-41cc-b3dd-bb5349d6cd0f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_637abe6a-e8ae-4c09-9acc-b75c6a03e1bf" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_d8cc33f7-bc13-4b39-b707-5a1951a5a22c" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_637abe6a-e8ae-4c09-9acc-b75c6a03e1bf" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentsFairValueDisclosure_f5e7b924-44bc-465a-8cb4-a8881459d0d9" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InvestmentsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_d8cc33f7-bc13-4b39-b707-5a1951a5a22c" xlink:to="loc_us-gaap_InvestmentsFairValueDisclosure_f5e7b924-44bc-465a-8cb4-a8881459d0d9" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_5490a729-defc-4e7a-9d51-78001cb68563" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtSecuritiesAvailableForSaleTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_d8cc33f7-bc13-4b39-b707-5a1951a5a22c" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_5490a729-defc-4e7a-9d51-78001cb68563" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeAxis_0d63d88a-88ef-4be1-8751-9c356a352d15" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InvestmentTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_5490a729-defc-4e7a-9d51-78001cb68563" xlink:to="loc_us-gaap_InvestmentTypeAxis_0d63d88a-88ef-4be1-8751-9c356a352d15" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeCategorizationMember_0d63d88a-88ef-4be1-8751-9c356a352d15_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InvestmentTypeCategorizationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_InvestmentTypeAxis_0d63d88a-88ef-4be1-8751-9c356a352d15" xlink:to="loc_us-gaap_InvestmentTypeCategorizationMember_0d63d88a-88ef-4be1-8751-9c356a352d15_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeCategorizationMember_edd8cadd-5e22-4641-a6b2-1eded4248a35" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InvestmentTypeCategorizationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_InvestmentTypeAxis_0d63d88a-88ef-4be1-8751-9c356a352d15" xlink:to="loc_us-gaap_InvestmentTypeCategorizationMember_edd8cadd-5e22-4641-a6b2-1eded4248a35" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermInvestmentsMember_46419cc5-0296-40fd-b588-2f7a68fb1ad0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShortTermInvestmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_edd8cadd-5e22-4641-a6b2-1eded4248a35" xlink:to="loc_us-gaap_ShortTermInvestmentsMember_46419cc5-0296-40fd-b588-2f7a68fb1ad0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLongTermInvestmentsMember_0b8f2658-6551-4ed3-9b9b-9b7bb41cbd13" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherLongTermInvestmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_edd8cadd-5e22-4641-a6b2-1eded4248a35" xlink:to="loc_us-gaap_OtherLongTermInvestmentsMember_0b8f2658-6551-4ed3-9b9b-9b7bb41cbd13" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_3906882e-bd0a-44d5-bde4-2dc45b5ca6d2" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtSecuritiesAvailableForSaleTable_5490a729-defc-4e7a-9d51-78001cb68563" xlink:to="loc_us-gaap_FinancialInstrumentAxis_3906882e-bd0a-44d5-bde4-2dc45b5ca6d2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_3906882e-bd0a-44d5-bde4-2dc45b5ca6d2_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_3906882e-bd0a-44d5-bde4-2dc45b5ca6d2" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_3906882e-bd0a-44d5-bde4-2dc45b5ca6d2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_814f5366-562c-4e99-a67f-71e4e1d52e91" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_3906882e-bd0a-44d5-bde4-2dc45b5ca6d2" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_814f5366-562c-4e99-a67f-71e4e1d52e91" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CertificatesOfDepositMember_390d2337-f1cb-4c86-8b79-c3ce529302f9" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CertificatesOfDepositMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_814f5366-562c-4e99-a67f-71e4e1d52e91" xlink:to="loc_us-gaap_CertificatesOfDepositMember_390d2337-f1cb-4c86-8b79-c3ce529302f9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateBondSecuritiesMember_37f67061-6f72-458b-acff-626e19bbbac7" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CorporateBondSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_814f5366-562c-4e99-a67f-71e4e1d52e91" xlink:to="loc_us-gaap_CorporateBondSecuritiesMember_37f67061-6f72-458b-acff-626e19bbbac7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USTreasurySecuritiesMember_9cac15d9-e705-42d1-a9f3-fde8225da9d3" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_USTreasurySecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_814f5366-562c-4e99-a67f-71e4e1d52e91" xlink:to="loc_us-gaap_USTreasurySecuritiesMember_9cac15d9-e705-42d1-a9f3-fde8225da9d3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MunicipalBondsMember_58855394-67d6-49a6-a25f-dd2aba5c10a5" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_MunicipalBondsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_814f5366-562c-4e99-a67f-71e4e1d52e91" xlink:to="loc_us-gaap_MunicipalBondsMember_58855394-67d6-49a6-a25f-dd2aba5c10a5" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherDebtSecuritiesMember_e288632d-6484-4f13-ac8d-bab2fcb78d30" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherDebtSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_814f5366-562c-4e99-a67f-71e4e1d52e91" xlink:to="loc_us-gaap_OtherDebtSecuritiesMember_e288632d-6484-4f13-ac8d-bab2fcb78d30" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetBackedSecuritiesMember_93445435-5253-4959-8e23-bb940a58d913" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AssetBackedSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_814f5366-562c-4e99-a67f-71e4e1d52e91" xlink:to="loc_us-gaap_AssetBackedSecuritiesMember_93445435-5253-4959-8e23-bb940a58d913" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.gentex.com/role/InvestmentsScheduleofUnrealizedLossonInvestmentsDetails" xlink:type="simple" xlink:href="gntx-20200630.xsd#InvestmentsScheduleofUnrealizedLossonInvestmentsDetails"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/InvestmentsScheduleofUnrealizedLossonInvestmentsDetails" xlink:type="extended" id="ib65853f1b8ed41328df0b31faebb3fe4_InvestmentsScheduleofUnrealizedLossonInvestmentsDetails"/>
  <link:roleRef roleURI="http://www.gentex.com/role/InvestmentsInvestmentsClassifiedbyContractualMaturityDateDetails" xlink:type="simple" xlink:href="gntx-20200630.xsd#InvestmentsInvestmentsClassifiedbyContractualMaturityDateDetails"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/InvestmentsInvestmentsClassifiedbyContractualMaturityDateDetails" xlink:type="extended" id="id55321c97cb24ac6af740f020e0d8a3f_InvestmentsInvestmentsClassifiedbyContractualMaturityDateDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_8ca160ad-575e-4dcf-8fd2-6860bd2bb0bd" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue_a99fe6f7-c19f-49e3-93a5-8343c0f37bdc" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_8ca160ad-575e-4dcf-8fd2-6860bd2bb0bd" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue_a99fe6f7-c19f-49e3-93a5-8343c0f37bdc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue_ae6fb095-41e7-4782-b398-e65eea7c39af" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_8ca160ad-575e-4dcf-8fd2-6860bd2bb0bd" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesAfterOneThroughFiveYearsFairValue_ae6fb095-41e7-4782-b398-e65eea7c39af" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_DebtSecuritiesAvailableForSaleMaturityAllocatedAndSingleMaturityDateAfterFiveYearsFairValue_42af36c1-9969-410a-8eae-76a595a2dec9" xlink:href="gntx-20200630.xsd#gntx_DebtSecuritiesAvailableForSaleMaturityAllocatedAndSingleMaturityDateAfterFiveYearsFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_8ca160ad-575e-4dcf-8fd2-6860bd2bb0bd" xlink:to="loc_gntx_DebtSecuritiesAvailableForSaleMaturityAllocatedAndSingleMaturityDateAfterFiveYearsFairValue_42af36c1-9969-410a-8eae-76a595a2dec9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_5e107086-129e-4a4c-867b-3d8322ac7ccb" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_8ca160ad-575e-4dcf-8fd2-6860bd2bb0bd" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_5e107086-129e-4a4c-867b-3d8322ac7ccb" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesTable_a0009226-f7a5-4c85-81cb-a152fd297321" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfAvailableForSaleSecuritiesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_8ca160ad-575e-4dcf-8fd2-6860bd2bb0bd" xlink:to="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesTable_a0009226-f7a5-4c85-81cb-a152fd297321" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_b0848b15-b87c-454e-93fe-601c82e9a7e8" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesTable_a0009226-f7a5-4c85-81cb-a152fd297321" xlink:to="loc_us-gaap_FinancialInstrumentAxis_b0848b15-b87c-454e-93fe-601c82e9a7e8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_b0848b15-b87c-454e-93fe-601c82e9a7e8_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_b0848b15-b87c-454e-93fe-601c82e9a7e8" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_b0848b15-b87c-454e-93fe-601c82e9a7e8_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_a1dd0229-feec-4ea3-80bd-fdb3e6d53825" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_b0848b15-b87c-454e-93fe-601c82e9a7e8" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_a1dd0229-feec-4ea3-80bd-fdb3e6d53825" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FixedIncomeSecuritiesMember_9be0d7ca-4213-490f-be83-82f764899aad" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FixedIncomeSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_a1dd0229-feec-4ea3-80bd-fdb3e6d53825" xlink:to="loc_us-gaap_FixedIncomeSecuritiesMember_9be0d7ca-4213-490f-be83-82f764899aad" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.gentex.com/role/Inventories" xlink:type="simple" xlink:href="gntx-20200630.xsd#Inventories"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/Inventories" xlink:type="extended" id="i4573356d40a942549e41b3b9fc3875ac_Inventories"/>
  <link:roleRef roleURI="http://www.gentex.com/role/InventoriesTables" xlink:type="simple" xlink:href="gntx-20200630.xsd#InventoriesTables"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/InventoriesTables" xlink:type="extended" id="ied9b21cd27e54ed9911b457fc646b99c_InventoriesTables"/>
  <link:roleRef roleURI="http://www.gentex.com/role/InventoriesScheduleofInventoriesDetails" xlink:type="simple" xlink:href="gntx-20200630.xsd#InventoriesScheduleofInventoriesDetails"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/InventoriesScheduleofInventoriesDetails" xlink:type="extended" id="idb84fa45f24c4cb5b312ca14dbbf9fe6_InventoriesScheduleofInventoriesDetails"/>
  <link:roleRef roleURI="http://www.gentex.com/role/EarningsPerShare" xlink:type="simple" xlink:href="gntx-20200630.xsd#EarningsPerShare"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/EarningsPerShare" xlink:type="extended" id="i6b7b184b04a1492786abd69f1b805983_EarningsPerShare"/>
  <link:roleRef roleURI="http://www.gentex.com/role/EarningsPerShareTables" xlink:type="simple" xlink:href="gntx-20200630.xsd#EarningsPerShareTables"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/EarningsPerShareTables" xlink:type="extended" id="ie23d83711e184cc9bbbd864552fe60d4_EarningsPerShareTables"/>
  <link:roleRef roleURI="http://www.gentex.com/role/EarningsPerShareScheduleofEarningsPerShareBasicandDilutedDetails" xlink:type="simple" xlink:href="gntx-20200630.xsd#EarningsPerShareScheduleofEarningsPerShareBasicandDilutedDetails"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/EarningsPerShareScheduleofEarningsPerShareBasicandDilutedDetails" xlink:type="extended" id="i47a7fff21b0f4d06a3878f5f501f8c8c_EarningsPerShareScheduleofEarningsPerShareBasicandDilutedDetails"/>
  <link:roleRef roleURI="http://www.gentex.com/role/StockBasedCompensationPlans" xlink:type="simple" xlink:href="gntx-20200630.xsd#StockBasedCompensationPlans"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/StockBasedCompensationPlans" xlink:type="extended" id="i4d637f8281514ad9a027c1d21a3bdce0_StockBasedCompensationPlans"/>
  <link:roleRef roleURI="http://www.gentex.com/role/StockBasedCompensationPlansTables" xlink:type="simple" xlink:href="gntx-20200630.xsd#StockBasedCompensationPlansTables"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/StockBasedCompensationPlansTables" xlink:type="extended" id="idc3f94e6693e4f928f2c000eefa8a9fe_StockBasedCompensationPlansTables"/>
  <link:roleRef roleURI="http://www.gentex.com/role/StockBasedCompensationPlansNarrativeDetails" xlink:type="simple" xlink:href="gntx-20200630.xsd#StockBasedCompensationPlansNarrativeDetails"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/StockBasedCompensationPlansNarrativeDetails" xlink:type="extended" id="i50cfe307fcbf455d9730951bc9b42d0a_StockBasedCompensationPlansNarrativeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_b4fcb5e4-4b64-4f76-98de-91cfb88e5696" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_SharebasedCompensationArrangementbySharebasedPaymentAwardNumberOfPlans_d806c31a-af78-43d3-a4ef-2e2e1f1057f1" xlink:href="gntx-20200630.xsd#gntx_SharebasedCompensationArrangementbySharebasedPaymentAwardNumberOfPlans"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_b4fcb5e4-4b64-4f76-98de-91cfb88e5696" xlink:to="loc_gntx_SharebasedCompensationArrangementbySharebasedPaymentAwardNumberOfPlans_d806c31a-af78-43d3-a4ef-2e2e1f1057f1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensation_6bd7fcd6-390a-445b-9895-315c879618d2" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_b4fcb5e4-4b64-4f76-98de-91cfb88e5696" xlink:to="loc_us-gaap_ShareBasedCompensation_6bd7fcd6-390a-445b-9895-315c879618d2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_7c1229ea-b023-49ef-8fee-26b6d4d23994" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AllocatedShareBasedCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_b4fcb5e4-4b64-4f76-98de-91cfb88e5696" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_7c1229ea-b023-49ef-8fee-26b6d4d23994" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized_20ba1ab5-490e-409f-9816-2ac3ca2364ec" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_b4fcb5e4-4b64-4f76-98de-91cfb88e5696" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized_20ba1ab5-490e-409f-9816-2ac3ca2364ec" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod_70418419-796d-4f97-aaa2-39eb81081747" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_b4fcb5e4-4b64-4f76-98de-91cfb88e5696" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod_70418419-796d-4f97-aaa2-39eb81081747" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_306885c0-2cc5-42b3-b137-f3c9072b684a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_b4fcb5e4-4b64-4f76-98de-91cfb88e5696" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_306885c0-2cc5-42b3-b137-f3c9072b684a" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2_f1810f0a-997b-41a5-82c7-f54a220b7501" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_b4fcb5e4-4b64-4f76-98de-91cfb88e5696" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageRemainingContractualTerm2_f1810f0a-997b-41a5-82c7-f54a220b7501" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_844c28c8-d89e-40f3-a67a-5ad84de0fcef" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_b4fcb5e4-4b64-4f76-98de-91cfb88e5696" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_844c28c8-d89e-40f3-a67a-5ad84de0fcef" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_ShareBasedCompensationRestrictedPeriod_9a46fd2b-94e3-40e8-b6d0-00c8d3f0bbbe" xlink:href="gntx-20200630.xsd#gntx_ShareBasedCompensationRestrictedPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_b4fcb5e4-4b64-4f76-98de-91cfb88e5696" xlink:to="loc_gntx_ShareBasedCompensationRestrictedPeriod_9a46fd2b-94e3-40e8-b6d0-00c8d3f0bbbe" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockExpense_50c9d545-54e6-4305-b31f-6e2fe3000d39" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RestrictedStockExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_b4fcb5e4-4b64-4f76-98de-91cfb88e5696" xlink:to="loc_us-gaap_RestrictedStockExpense_50c9d545-54e6-4305-b31f-6e2fe3000d39" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockOwnershipPlanESOPSharesInESOP_f0366dcc-f79b-42bc-bc87-6dff43b2c7a3" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EmployeeStockOwnershipPlanESOPSharesInESOP"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_b4fcb5e4-4b64-4f76-98de-91cfb88e5696" xlink:to="loc_us-gaap_EmployeeStockOwnershipPlanESOPSharesInESOP_f0366dcc-f79b-42bc-bc87-6dff43b2c7a3" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardDiscountFromMarketPricePurchaseDate_899b8e09-b61b-4e48-a999-f7689b3e60f7" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardDiscountFromMarketPricePurchaseDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_b4fcb5e4-4b64-4f76-98de-91cfb88e5696" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardDiscountFromMarketPricePurchaseDate_899b8e09-b61b-4e48-a999-f7689b3e60f7" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_ShareBasedCompensationArrangementByShareBasedPaymentAwardDiscountRecognizedAsCompensationExpense_5cda2371-b98b-49e2-9f33-f9cbf1a8be64" xlink:href="gntx-20200630.xsd#gntx_ShareBasedCompensationArrangementByShareBasedPaymentAwardDiscountRecognizedAsCompensationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_b4fcb5e4-4b64-4f76-98de-91cfb88e5696" xlink:to="loc_gntx_ShareBasedCompensationArrangementByShareBasedPaymentAwardDiscountRecognizedAsCompensationExpense_5cda2371-b98b-49e2-9f33-f9cbf1a8be64" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockOwnershipPlanESOPNumberOfAllocatedShares_ad6c5579-7cad-4ebe-aed9-5f94411b6f96" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EmployeeStockOwnershipPlanESOPNumberOfAllocatedShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_b4fcb5e4-4b64-4f76-98de-91cfb88e5696" xlink:to="loc_us-gaap_EmployeeStockOwnershipPlanESOPNumberOfAllocatedShares_ad6c5579-7cad-4ebe-aed9-5f94411b6f96" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_3eb44ab7-4399-4d83-a8bd-a403277bf988" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_b4fcb5e4-4b64-4f76-98de-91cfb88e5696" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_3eb44ab7-4399-4d83-a8bd-a403277bf988" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_c98cc55c-bf80-472c-8db5-b6d884aae65d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_3eb44ab7-4399-4d83-a8bd-a403277bf988" xlink:to="loc_us-gaap_AwardTypeAxis_c98cc55c-bf80-472c-8db5-b6d884aae65d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_c98cc55c-bf80-472c-8db5-b6d884aae65d_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_c98cc55c-bf80-472c-8db5-b6d884aae65d" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_c98cc55c-bf80-472c-8db5-b6d884aae65d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_c0b0aa2d-69ee-4ba1-8f93-5dddbea217b4" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_c98cc55c-bf80-472c-8db5-b6d884aae65d" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_c0b0aa2d-69ee-4ba1-8f93-5dddbea217b4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockCompensationPlanMember_2caf66b4-1fde-478c-8e66-b1082b028c3a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockCompensationPlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_c0b0aa2d-69ee-4ba1-8f93-5dddbea217b4" xlink:to="loc_us-gaap_StockCompensationPlanMember_2caf66b4-1fde-478c-8e66-b1082b028c3a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PerformanceSharesMember_2e59e791-585d-499c-913c-349fa0bac335" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PerformanceSharesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_c0b0aa2d-69ee-4ba1-8f93-5dddbea217b4" xlink:to="loc_us-gaap_PerformanceSharesMember_2e59e791-585d-499c-913c-349fa0bac335" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameAxis_b67b1ff3-4e7e-4b39-ac22-6837602d2a51" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PlanNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_3eb44ab7-4399-4d83-a8bd-a403277bf988" xlink:to="loc_us-gaap_PlanNameAxis_b67b1ff3-4e7e-4b39-ac22-6837602d2a51" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_b67b1ff3-4e7e-4b39-ac22-6837602d2a51_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PlanNameAxis_b67b1ff3-4e7e-4b39-ac22-6837602d2a51" xlink:to="loc_us-gaap_PlanNameDomain_b67b1ff3-4e7e-4b39-ac22-6837602d2a51_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_07a0f6dc-3eee-4310-b097-dfe8805aaf13" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PlanNameAxis_b67b1ff3-4e7e-4b39-ac22-6837602d2a51" xlink:to="loc_us-gaap_PlanNameDomain_07a0f6dc-3eee-4310-b097-dfe8805aaf13" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_OmnibusIncentivePlanMember_6b1331d8-b27d-42a0-b0ad-66ac96b0b517" xlink:href="gntx-20200630.xsd#gntx_OmnibusIncentivePlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_07a0f6dc-3eee-4310-b097-dfe8805aaf13" xlink:to="loc_gntx_OmnibusIncentivePlanMember_6b1331d8-b27d-42a0-b0ad-66ac96b0b517" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_EmployeeStockOptionPlanMember_ec3b1044-e090-4d9e-8d43-fe3c2b8461e6" xlink:href="gntx-20200630.xsd#gntx_EmployeeStockOptionPlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_07a0f6dc-3eee-4310-b097-dfe8805aaf13" xlink:to="loc_gntx_EmployeeStockOptionPlanMember_ec3b1044-e090-4d9e-8d43-fe3c2b8461e6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_RestrictedStockPlanMember_3c05e374-8296-4450-8190-27de7a742a03" xlink:href="gntx-20200630.xsd#gntx_RestrictedStockPlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_07a0f6dc-3eee-4310-b097-dfe8805aaf13" xlink:to="loc_gntx_RestrictedStockPlanMember_3c05e374-8296-4450-8190-27de7a742a03" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_EmployeeStockPurchasePlanMember_244f6045-c2de-4d12-b782-7a7733d6b779" xlink:href="gntx-20200630.xsd#gntx_EmployeeStockPurchasePlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_07a0f6dc-3eee-4310-b097-dfe8805aaf13" xlink:to="loc_gntx_EmployeeStockPurchasePlanMember_244f6045-c2de-4d12-b782-7a7733d6b779" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_4be26996-205d-4373-976b-50907588d9a7" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_3eb44ab7-4399-4d83-a8bd-a403277bf988" xlink:to="loc_srt_RangeAxis_4be26996-205d-4373-976b-50907588d9a7" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_4be26996-205d-4373-976b-50907588d9a7_default" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_4be26996-205d-4373-976b-50907588d9a7" xlink:to="loc_srt_RangeMember_4be26996-205d-4373-976b-50907588d9a7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_f027f742-2be7-4417-8831-56a809cbd7e0" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_4be26996-205d-4373-976b-50907588d9a7" xlink:to="loc_srt_RangeMember_f027f742-2be7-4417-8831-56a809cbd7e0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_ebf8ece4-9e45-4b13-9a36-5615b957cced" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_f027f742-2be7-4417-8831-56a809cbd7e0" xlink:to="loc_srt_MinimumMember_ebf8ece4-9e45-4b13-9a36-5615b957cced" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_39445723-8775-42d3-adc7-8901d34d631e" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_f027f742-2be7-4417-8831-56a809cbd7e0" xlink:to="loc_srt_MaximumMember_39445723-8775-42d3-adc7-8901d34d631e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringCostAndReserveAxis_1fd069d8-2203-4103-974f-0cd1d209925d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RestructuringCostAndReserveAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_3eb44ab7-4399-4d83-a8bd-a403277bf988" xlink:to="loc_us-gaap_RestructuringCostAndReserveAxis_1fd069d8-2203-4103-974f-0cd1d209925d" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TypeOfRestructuringDomain_1fd069d8-2203-4103-974f-0cd1d209925d_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TypeOfRestructuringDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RestructuringCostAndReserveAxis_1fd069d8-2203-4103-974f-0cd1d209925d" xlink:to="loc_us-gaap_TypeOfRestructuringDomain_1fd069d8-2203-4103-974f-0cd1d209925d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TypeOfRestructuringDomain_0975096a-4e7b-4282-aafc-4ad634026986" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TypeOfRestructuringDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RestructuringCostAndReserveAxis_1fd069d8-2203-4103-974f-0cd1d209925d" xlink:to="loc_us-gaap_TypeOfRestructuringDomain_0975096a-4e7b-4282-aafc-4ad634026986" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeSeveranceMember_4a22f0c5-b30a-4acd-a7bd-ee4ae7333a51" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EmployeeSeveranceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TypeOfRestructuringDomain_0975096a-4e7b-4282-aafc-4ad634026986" xlink:to="loc_us-gaap_EmployeeSeveranceMember_4a22f0c5-b30a-4acd-a7bd-ee4ae7333a51" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.gentex.com/role/StockBasedCompensationPlansWeightedAverageAssumptionsfortheESOPDetails" xlink:type="simple" xlink:href="gntx-20200630.xsd#StockBasedCompensationPlansWeightedAverageAssumptionsfortheESOPDetails"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/StockBasedCompensationPlansWeightedAverageAssumptionsfortheESOPDetails" xlink:type="extended" id="ic6c975e92a8a449dbc0b63d050081c0c_StockBasedCompensationPlansWeightedAverageAssumptionsfortheESOPDetails"/>
  <link:roleRef roleURI="http://www.gentex.com/role/ComprehensiveIncome" xlink:type="simple" xlink:href="gntx-20200630.xsd#ComprehensiveIncome"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/ComprehensiveIncome" xlink:type="extended" id="ie1e112cfaf1443a0b8d0b96801098e14_ComprehensiveIncome"/>
  <link:roleRef roleURI="http://www.gentex.com/role/ComprehensiveIncomeTables" xlink:type="simple" xlink:href="gntx-20200630.xsd#ComprehensiveIncomeTables"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/ComprehensiveIncomeTables" xlink:type="extended" id="ic6404341bfae43b9a83df173d24bc9aa_ComprehensiveIncomeTables"/>
  <link:roleRef roleURI="http://www.gentex.com/role/ComprehensiveIncomeAOCIRollforwardDetails" xlink:type="simple" xlink:href="gntx-20200630.xsd#ComprehensiveIncomeAOCIRollforwardDetails"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/ComprehensiveIncomeAOCIRollforwardDetails" xlink:type="extended" id="iee5f9195155240069894e1f5d72bfb26_ComprehensiveIncomeAOCIRollforwardDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_8e321fee-4152-4ac0-b261-8e346660de2d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_b9b7a34f-99e3-4ccb-acdd-611a8a0d24ad" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AOCIAttributableToParentNetOfTaxRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_8e321fee-4152-4ac0-b261-8e346660de2d" xlink:to="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_b9b7a34f-99e3-4ccb-acdd-611a8a0d24ad" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_c990e0c1-932b-4760-82d5-331e4a89a48e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_b9b7a34f-99e3-4ccb-acdd-611a8a0d24ad" xlink:to="loc_us-gaap_StockholdersEquity_c990e0c1-932b-4760-82d5-331e4a89a48e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax_ccccb915-4dd6-4366-ab5f-465b4e80b7cb" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_b9b7a34f-99e3-4ccb-acdd-611a8a0d24ad" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax_ccccb915-4dd6-4366-ab5f-465b4e80b7cb" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ComprehensiveIncomeNetOfTax_4ca37dbd-0cf9-4fa9-902b-890dd285e99f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ComprehensiveIncomeNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_b9b7a34f-99e3-4ccb-acdd-611a8a0d24ad" xlink:to="loc_us-gaap_ComprehensiveIncomeNetOfTax_4ca37dbd-0cf9-4fa9-902b-890dd285e99f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax_d6dfa099-12d1-441b-a347-88729f49f220" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_b9b7a34f-99e3-4ccb-acdd-611a8a0d24ad" xlink:to="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax_d6dfa099-12d1-441b-a347-88729f49f220" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_e312a7bb-2119-43d5-9df1-bb238468ee0f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StockholdersEquity"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_8cfeb7a1-75ff-47fa-878d-0adb8bbe36d7" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AOCIAttributableToParentNetOfTaxRollForward_b9b7a34f-99e3-4ccb-acdd-611a8a0d24ad" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_8cfeb7a1-75ff-47fa-878d-0adb8bbe36d7" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_7f2d7eb3-59c6-4042-ba10-0430831d4c49" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_8e321fee-4152-4ac0-b261-8e346660de2d" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_7f2d7eb3-59c6-4042-ba10-0430831d4c49" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_d35da8e5-fc00-45d2-a279-f9b99622713f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_7f2d7eb3-59c6-4042-ba10-0430831d4c49" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_d35da8e5-fc00-45d2-a279-f9b99622713f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_d35da8e5-fc00-45d2-a279-f9b99622713f_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_d35da8e5-fc00-45d2-a279-f9b99622713f" xlink:to="loc_us-gaap_EquityComponentDomain_d35da8e5-fc00-45d2-a279-f9b99622713f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_87638d7a-7631-4ac6-a7f8-dc72f34bf727" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_d35da8e5-fc00-45d2-a279-f9b99622713f" xlink:to="loc_us-gaap_EquityComponentDomain_87638d7a-7631-4ac6-a7f8-dc72f34bf727" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_c3519871-8c90-4161-8849-f1c5f8a1b53f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_87638d7a-7631-4ac6-a7f8-dc72f34bf727" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_c3519871-8c90-4161-8849-f1c5f8a1b53f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedTranslationAdjustmentMember_421ea4dd-91a4-4094-9f53-2e069245a442" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccumulatedTranslationAdjustmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_c3519871-8c90-4161-8849-f1c5f8a1b53f" xlink:to="loc_us-gaap_AccumulatedTranslationAdjustmentMember_421ea4dd-91a4-4094-9f53-2e069245a442" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember_eed92ae5-e387-4887-822c-9a1b854bf434" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_c3519871-8c90-4161-8849-f1c5f8a1b53f" xlink:to="loc_us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember_eed92ae5-e387-4887-822c-9a1b854bf434" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.gentex.com/role/ComprehensiveIncomeReclassificationOutofAccumulatedOtherComprehensiveIncomeDetails" xlink:type="simple" xlink:href="gntx-20200630.xsd#ComprehensiveIncomeReclassificationOutofAccumulatedOtherComprehensiveIncomeDetails"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/ComprehensiveIncomeReclassificationOutofAccumulatedOtherComprehensiveIncomeDetails" xlink:type="extended" id="ie76fd7c1dfde46c59067c305527983a8_ComprehensiveIncomeReclassificationOutofAccumulatedOtherComprehensiveIncomeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncomeLineItems_dba4548c-73b7-4e8b-88fc-73b00d5018d8" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncomeLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesFvNiRealizedGainLoss_0e435ca2-24eb-4581-9120-fbf8be917918" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquitySecuritiesFvNiRealizedGainLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncomeLineItems_dba4548c-73b7-4e8b-88fc-73b00d5018d8" xlink:to="loc_us-gaap_EquitySecuritiesFvNiRealizedGainLoss_0e435ca2-24eb-4581-9120-fbf8be917918" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_89ea3d61-9b97-4ae6-8155-993098bd788f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeTaxExpenseBenefit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncomeLineItems_dba4548c-73b7-4e8b-88fc-73b00d5018d8" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_89ea3d61-9b97-4ae6-8155-993098bd788f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss_e371b732-8375-4897-84fa-a2834dcadb1d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ProfitLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncomeLineItems_dba4548c-73b7-4e8b-88fc-73b00d5018d8" xlink:to="loc_us-gaap_ProfitLoss_e371b732-8375-4897-84fa-a2834dcadb1d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeTable_eed42929-9925-4689-a777-85b82411ceb1" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ReclassificationAdjustmentOutOfAccumulatedOtherComprehensiveIncomeLineItems_dba4548c-73b7-4e8b-88fc-73b00d5018d8" xlink:to="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeTable_eed42929-9925-4689-a777-85b82411ceb1" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis_8328b129-8820-4708-a05f-074526649ee2" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeTable_eed42929-9925-4689-a777-85b82411ceb1" xlink:to="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis_8328b129-8820-4708-a05f-074526649ee2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeDomain_8328b129-8820-4708-a05f-074526649ee2_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis_8328b129-8820-4708-a05f-074526649ee2" xlink:to="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeDomain_8328b129-8820-4708-a05f-074526649ee2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeDomain_5ed25ea9-408d-4d61-b15b-3eb20d63f662" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeAxis_8328b129-8820-4708-a05f-074526649ee2" xlink:to="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeDomain_5ed25ea9-408d-4d61-b15b-3eb20d63f662" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember_059fa3f1-874c-4c9e-b3ee-be92d5f78869" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeDomain_5ed25ea9-408d-4d61-b15b-3eb20d63f662" xlink:to="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeMember_059fa3f1-874c-4c9e-b3ee-be92d5f78869" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_030a71a6-5657-4144-a018-542d43f8133f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ReclassificationOutOfAccumulatedOtherComprehensiveIncomeTable_eed42929-9925-4689-a777-85b82411ceb1" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_030a71a6-5657-4144-a018-542d43f8133f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_030a71a6-5657-4144-a018-542d43f8133f_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_030a71a6-5657-4144-a018-542d43f8133f" xlink:to="loc_us-gaap_EquityComponentDomain_030a71a6-5657-4144-a018-542d43f8133f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_6714cbf8-c9eb-4410-9f0b-f25866f5fb11" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_030a71a6-5657-4144-a018-542d43f8133f" xlink:to="loc_us-gaap_EquityComponentDomain_6714cbf8-c9eb-4410-9f0b-f25866f5fb11" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember_38506a25-d940-4bff-9557-c1e3a117601b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_6714cbf8-c9eb-4410-9f0b-f25866f5fb11" xlink:to="loc_us-gaap_AccumulatedNetUnrealizedInvestmentGainLossMember_38506a25-d940-4bff-9557-c1e3a117601b" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.gentex.com/role/DebtandFinancingArrangements" xlink:type="simple" xlink:href="gntx-20200630.xsd#DebtandFinancingArrangements"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/DebtandFinancingArrangements" xlink:type="extended" id="ib75068dac6174c7eb6dc001b472c78d0_DebtandFinancingArrangements"/>
  <link:roleRef roleURI="http://www.gentex.com/role/DebtandFinancingArrangementsDetails" xlink:type="simple" xlink:href="gntx-20200630.xsd#DebtandFinancingArrangementsDetails"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/DebtandFinancingArrangementsDetails" xlink:type="extended" id="ic2e1599253884fa490369938e613c696_DebtandFinancingArrangementsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_9f07f633-166d-4b6d-a4e7-d24be0c1e4f4" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_7753d195-86c6-4e33-97d7-6b103b60df4f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_9f07f633-166d-4b6d-a4e7-d24be0c1e4f4" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_7753d195-86c6-4e33-97d7-6b103b60df4f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_DebtInstrumentAdditionalBorrowingsAvailableFaceAmount_39dbdad4-416a-48fc-bb98-200f3e0ae03c" xlink:href="gntx-20200630.xsd#gntx_DebtInstrumentAdditionalBorrowingsAvailableFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_9f07f633-166d-4b6d-a4e7-d24be0c1e4f4" xlink:to="loc_gntx_DebtInstrumentAdditionalBorrowingsAvailableFaceAmount_39dbdad4-416a-48fc-bb98-200f3e0ae03c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_3a927e08-db00-444b-93d1-9773c9bb7747" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_9f07f633-166d-4b6d-a4e7-d24be0c1e4f4" xlink:to="loc_us-gaap_LongTermDebt_3a927e08-db00-444b-93d1-9773c9bb7747" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateDuringPeriod_2befd050-a863-46f3-90e5-29e6e8f38b7e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentInterestRateDuringPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_9f07f633-166d-4b6d-a4e7-d24be0c1e4f4" xlink:to="loc_us-gaap_DebtInstrumentInterestRateDuringPeriod_2befd050-a863-46f3-90e5-29e6e8f38b7e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpenseDebt_cf835bff-0b67-4363-b08f-0dc23011ea4d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InterestExpenseDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_9f07f633-166d-4b6d-a4e7-d24be0c1e4f4" xlink:to="loc_us-gaap_InterestExpenseDebt_cf835bff-0b67-4363-b08f-0dc23011ea4d" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateIncreaseDecrease_29632b75-b987-4cce-9d0f-76840d0a0b12" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentInterestRateIncreaseDecrease"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_9f07f633-166d-4b6d-a4e7-d24be0c1e4f4" xlink:to="loc_us-gaap_DebtInstrumentInterestRateIncreaseDecrease_29632b75-b987-4cce-9d0f-76840d0a0b12" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_InterestExpenseDebtAnnualIncrease_b92af88e-a0e6-48a2-ae13-673113b9fcdd" xlink:href="gntx-20200630.xsd#gntx_InterestExpenseDebtAnnualIncrease"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_9f07f633-166d-4b6d-a4e7-d24be0c1e4f4" xlink:to="loc_gntx_InterestExpenseDebtAnnualIncrease_b92af88e-a0e6-48a2-ae13-673113b9fcdd" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_ef132a12-05ac-4ecf-9c5d-7aa2eee38601" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_9f07f633-166d-4b6d-a4e7-d24be0c1e4f4" xlink:to="loc_us-gaap_DebtInstrumentTable_ef132a12-05ac-4ecf-9c5d-7aa2eee38601" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_808564b5-1808-4f31-8fae-4712641795f5" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_ef132a12-05ac-4ecf-9c5d-7aa2eee38601" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_808564b5-1808-4f31-8fae-4712641795f5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_808564b5-1808-4f31-8fae-4712641795f5_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_808564b5-1808-4f31-8fae-4712641795f5" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_808564b5-1808-4f31-8fae-4712641795f5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_6d6c0242-b784-49f6-8f1a-a1cda4498dc6" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_808564b5-1808-4f31-8fae-4712641795f5" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_6d6c0242-b784-49f6-8f1a-a1cda4498dc6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_7763c0a2-b9d4-4aa0-9a84-fe14d051db5e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_6d6c0242-b784-49f6-8f1a-a1cda4498dc6" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_7763c0a2-b9d4-4aa0-9a84-fe14d051db5e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditMember_8d7717f7-b22f-49e9-a088-f63067531136" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LineOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_6d6c0242-b784-49f6-8f1a-a1cda4498dc6" xlink:to="loc_us-gaap_LineOfCreditMember_8d7717f7-b22f-49e9-a088-f63067531136" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_SwingLoansMember_ca85c074-826a-42cd-94f8-ca5f91fe68dd" xlink:href="gntx-20200630.xsd#gntx_SwingLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_6d6c0242-b784-49f6-8f1a-a1cda4498dc6" xlink:to="loc_gntx_SwingLoansMember_ca85c074-826a-42cd-94f8-ca5f91fe68dd" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LetterOfCreditMember_02bc4b14-9cd6-4750-b6ed-a1d9e6b9eab7" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LetterOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_6d6c0242-b784-49f6-8f1a-a1cda4498dc6" xlink:to="loc_us-gaap_LetterOfCreditMember_02bc4b14-9cd6-4750-b6ed-a1d9e6b9eab7" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.gentex.com/role/Equity" xlink:type="simple" xlink:href="gntx-20200630.xsd#Equity"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/Equity" xlink:type="extended" id="i6b00c27b077e418ca7cfb00b2910b03b_Equity"/>
  <link:roleRef roleURI="http://www.gentex.com/role/EquityDetails" xlink:type="simple" xlink:href="gntx-20200630.xsd#EquityDetails"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/EquityDetails" xlink:type="extended" id="i5ce8ca56f6fc4b9684bd31f76f0b796e_EquityDetails"/>
  <link:roleRef roleURI="http://www.gentex.com/role/Contingencies" xlink:type="simple" xlink:href="gntx-20200630.xsd#Contingencies"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/Contingencies" xlink:type="extended" id="if0c7ff786ba141b29475b6ee8e97a2ff_Contingencies"/>
  <link:roleRef roleURI="http://www.gentex.com/role/SegmentReporting" xlink:type="simple" xlink:href="gntx-20200630.xsd#SegmentReporting"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/SegmentReporting" xlink:type="extended" id="id765c1a33167436b93378301d6d3721a_SegmentReporting"/>
  <link:roleRef roleURI="http://www.gentex.com/role/SegmentReportingTables" xlink:type="simple" xlink:href="gntx-20200630.xsd#SegmentReportingTables"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/SegmentReportingTables" xlink:type="extended" id="if8266f0945ef440ea711123730e0e3c0_SegmentReportingTables"/>
  <link:roleRef roleURI="http://www.gentex.com/role/SegmentReportingScheduleofAutomotiveandOtherSegmentReportingDetails" xlink:type="simple" xlink:href="gntx-20200630.xsd#SegmentReportingScheduleofAutomotiveandOtherSegmentReportingDetails"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/SegmentReportingScheduleofAutomotiveandOtherSegmentReportingDetails" xlink:type="extended" id="i03735a72631d4422b95067a72f000f97_SegmentReportingScheduleofAutomotiveandOtherSegmentReportingDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_693ae491-edda-4317-b2db-a2f24873b49c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax_a358a444-2742-4bde-9a59-4656bdc9cbdb" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_693ae491-edda-4317-b2db-a2f24873b49c" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax_a358a444-2742-4bde-9a59-4656bdc9cbdb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingIncomeLoss_f3f61b8e-ace5-48ce-bc48-08f8d8b548c0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_693ae491-edda-4317-b2db-a2f24873b49c" xlink:to="loc_us-gaap_OperatingIncomeLoss_f3f61b8e-ace5-48ce-bc48-08f8d8b548c0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_b5ed67df-efa2-433e-9e42-4328bb75bacd" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_693ae491-edda-4317-b2db-a2f24873b49c" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_b5ed67df-efa2-433e-9e42-4328bb75bacd" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_563db065-e0be-4901-8803-aaee213743f9" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_b5ed67df-efa2-433e-9e42-4328bb75bacd" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_563db065-e0be-4901-8803-aaee213743f9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_563db065-e0be-4901-8803-aaee213743f9_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_563db065-e0be-4901-8803-aaee213743f9" xlink:to="loc_us-gaap_SegmentDomain_563db065-e0be-4901-8803-aaee213743f9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_ba3e7180-b637-441e-bc78-b7b55b8b882a" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_563db065-e0be-4901-8803-aaee213743f9" xlink:to="loc_us-gaap_SegmentDomain_ba3e7180-b637-441e-bc78-b7b55b8b882a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_AutomotiveProductsSegmentMember_65d86b0a-5d90-4182-8e34-7e2aef36f4a9" xlink:href="gntx-20200630.xsd#gntx_AutomotiveProductsSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_ba3e7180-b637-441e-bc78-b7b55b8b882a" xlink:to="loc_gntx_AutomotiveProductsSegmentMember_65d86b0a-5d90-4182-8e34-7e2aef36f4a9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllOtherSegmentsMember_a36f10d2-a6d0-413e-b425-a25bfcd3a151" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AllOtherSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_ba3e7180-b637-441e-bc78-b7b55b8b882a" xlink:to="loc_us-gaap_AllOtherSegmentsMember_a36f10d2-a6d0-413e-b425-a25bfcd3a151" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.gentex.com/role/IncomeTaxes" xlink:type="simple" xlink:href="gntx-20200630.xsd#IncomeTaxes"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/IncomeTaxes" xlink:type="extended" id="i556f249d6ba6431785b4d059350abd17_IncomeTaxes"/>
  <link:roleRef roleURI="http://www.gentex.com/role/IncomeTaxesDetails" xlink:type="simple" xlink:href="gntx-20200630.xsd#IncomeTaxesDetails"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/IncomeTaxesDetails" xlink:type="extended" id="iad286e57bdac4a46bccc7cd5e8952482_IncomeTaxesDetails"/>
  <link:roleRef roleURI="http://www.gentex.com/role/Revenue" xlink:type="simple" xlink:href="gntx-20200630.xsd#Revenue"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/Revenue" xlink:type="extended" id="i9cfb550d156345f6a96bcbbec9ed7b7a_Revenue"/>
  <link:roleRef roleURI="http://www.gentex.com/role/RevenueTables" xlink:type="simple" xlink:href="gntx-20200630.xsd#RevenueTables"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/RevenueTables" xlink:type="extended" id="i0fa79e9b454a4a26ad69a1c514fa3b49_RevenueTables"/>
  <link:roleRef roleURI="http://www.gentex.com/role/RevenueDetails" xlink:type="simple" xlink:href="gntx-20200630.xsd#RevenueDetails"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/RevenueDetails" xlink:type="extended" id="i896392966abb40029e9075e1aaebc50f_RevenueDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_046cf9f5-98eb-4f47-9540-c1ee13138b91" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DisaggregationOfRevenueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax_87775a01-4a12-481d-bbce-80b654714e99" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_046cf9f5-98eb-4f47-9540-c1ee13138b91" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerIncludingAssessedTax_87775a01-4a12-481d-bbce-80b654714e99" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_2e781f36-88bf-489c-b589-4f96e1f72df9" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_DisaggregationOfRevenueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_046cf9f5-98eb-4f47-9540-c1ee13138b91" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_2e781f36-88bf-489c-b589-4f96e1f72df9" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_7023504b-0c1f-48c9-b65f-0a3f4c954543" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_2e781f36-88bf-489c-b589-4f96e1f72df9" xlink:to="loc_srt_StatementGeographicalAxis_7023504b-0c1f-48c9-b65f-0a3f4c954543" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_7023504b-0c1f-48c9-b65f-0a3f4c954543_default" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_7023504b-0c1f-48c9-b65f-0a3f4c954543" xlink:to="loc_srt_SegmentGeographicalDomain_7023504b-0c1f-48c9-b65f-0a3f4c954543_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_e961e8b4-5b45-4aa5-9b58-b529c1c4bd40" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_7023504b-0c1f-48c9-b65f-0a3f4c954543" xlink:to="loc_srt_SegmentGeographicalDomain_e961e8b4-5b45-4aa5-9b58-b529c1c4bd40" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_US_db05aed6-e178-4a4e-a80a-4e7cb306ec30" xlink:href="https://xbrl.sec.gov/country/2020/country-2020-01-31.xsd#country_US"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_e961e8b4-5b45-4aa5-9b58-b529c1c4bd40" xlink:to="loc_country_US_db05aed6-e178-4a4e-a80a-4e7cb306ec30" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_DE_86362799-240a-43e9-ad8d-da0bff94555b" xlink:href="https://xbrl.sec.gov/country/2020/country-2020-01-31.xsd#country_DE"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_e961e8b4-5b45-4aa5-9b58-b529c1c4bd40" xlink:to="loc_country_DE_86362799-240a-43e9-ad8d-da0bff94555b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_JP_60987ee5-2c8a-4c9f-b36e-9acb8f29bd9e" xlink:href="https://xbrl.sec.gov/country/2020/country-2020-01-31.xsd#country_JP"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_e961e8b4-5b45-4aa5-9b58-b529c1c4bd40" xlink:to="loc_country_JP_60987ee5-2c8a-4c9f-b36e-9acb8f29bd9e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_MX_01cd12b3-4b15-43de-a3c1-21ac83508cb3" xlink:href="https://xbrl.sec.gov/country/2020/country-2020-01-31.xsd#country_MX"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_e961e8b4-5b45-4aa5-9b58-b529c1c4bd40" xlink:to="loc_country_MX_01cd12b3-4b15-43de-a3c1-21ac83508cb3" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_OtherCountriesMember_d48ff087-709d-4389-9307-123bcaf6a90f" xlink:href="gntx-20200630.xsd#gntx_OtherCountriesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_e961e8b4-5b45-4aa5-9b58-b529c1c4bd40" xlink:to="loc_gntx_OtherCountriesMember_d48ff087-709d-4389-9307-123bcaf6a90f" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_6ee6e1a5-e5bd-4106-bb11-fc750bf3577e" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_2e781f36-88bf-489c-b589-4f96e1f72df9" xlink:to="loc_srt_ProductOrServiceAxis_6ee6e1a5-e5bd-4106-bb11-fc750bf3577e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_6ee6e1a5-e5bd-4106-bb11-fc750bf3577e_default" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_6ee6e1a5-e5bd-4106-bb11-fc750bf3577e" xlink:to="loc_srt_ProductsAndServicesDomain_6ee6e1a5-e5bd-4106-bb11-fc750bf3577e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_52720b46-c0e3-4f60-8e21-73c0c7759404" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_6ee6e1a5-e5bd-4106-bb11-fc750bf3577e" xlink:to="loc_srt_ProductsAndServicesDomain_52720b46-c0e3-4f60-8e21-73c0c7759404" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_AutomotiveProductsMember_d522afd3-b962-4ed6-b900-8a5b54d78f20" xlink:href="gntx-20200630.xsd#gntx_AutomotiveProductsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_52720b46-c0e3-4f60-8e21-73c0c7759404" xlink:to="loc_gntx_AutomotiveProductsMember_d522afd3-b962-4ed6-b900-8a5b54d78f20" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_AutomotiveMirrorsElectronicsMember_805a783d-ebf2-4d2d-af70-9a6f41f4a733" xlink:href="gntx-20200630.xsd#gntx_AutomotiveMirrorsElectronicsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_gntx_AutomotiveProductsMember_d522afd3-b962-4ed6-b900-8a5b54d78f20" xlink:to="loc_gntx_AutomotiveMirrorsElectronicsMember_805a783d-ebf2-4d2d-af70-9a6f41f4a733" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_HomeLinkModulesMember_890b3ec5-ea1f-4ab0-87e3-484586a33e69" xlink:href="gntx-20200630.xsd#gntx_HomeLinkModulesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_gntx_AutomotiveProductsMember_d522afd3-b962-4ed6-b900-8a5b54d78f20" xlink:to="loc_gntx_HomeLinkModulesMember_890b3ec5-ea1f-4ab0-87e3-484586a33e69" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_OtherProductsMember_4a503798-4e58-42aa-971a-9986b93fd34a" xlink:href="gntx-20200630.xsd#gntx_OtherProductsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_52720b46-c0e3-4f60-8e21-73c0c7759404" xlink:to="loc_gntx_OtherProductsMember_4a503798-4e58-42aa-971a-9986b93fd34a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_FireProtectionProductsMember_a0e38a7d-1bae-4923-99da-3dcf31252d59" xlink:href="gntx-20200630.xsd#gntx_FireProtectionProductsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_gntx_OtherProductsMember_4a503798-4e58-42aa-971a-9986b93fd34a" xlink:to="loc_gntx_FireProtectionProductsMember_a0e38a7d-1bae-4923-99da-3dcf31252d59" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_WindowsProductsMember_49074361-3d19-43c2-b322-f2272fbd388f" xlink:href="gntx-20200630.xsd#gntx_WindowsProductsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_gntx_OtherProductsMember_4a503798-4e58-42aa-971a-9986b93fd34a" xlink:to="loc_gntx_WindowsProductsMember_49074361-3d19-43c2-b322-f2272fbd388f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_8925676e-e2d8-4f7c-9970-890f39ad26b6" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_2e781f36-88bf-489c-b589-4f96e1f72df9" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_8925676e-e2d8-4f7c-9970-890f39ad26b6" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_8925676e-e2d8-4f7c-9970-890f39ad26b6_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_8925676e-e2d8-4f7c-9970-890f39ad26b6" xlink:to="loc_us-gaap_SegmentDomain_8925676e-e2d8-4f7c-9970-890f39ad26b6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_dd1c99e2-ab07-43db-a480-952cee410b6e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_8925676e-e2d8-4f7c-9970-890f39ad26b6" xlink:to="loc_us-gaap_SegmentDomain_dd1c99e2-ab07-43db-a480-952cee410b6e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_AutomotiveSegmentMember_643dd207-9417-4835-8960-33f6e0b717cc" xlink:href="gntx-20200630.xsd#gntx_AutomotiveSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_dd1c99e2-ab07-43db-a480-952cee410b6e" xlink:to="loc_gntx_AutomotiveSegmentMember_643dd207-9417-4835-8960-33f6e0b717cc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_OtherSegmentMember_32f879a9-01f4-4574-801e-40b53f95674e" xlink:href="gntx-20200630.xsd#gntx_OtherSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_dd1c99e2-ab07-43db-a480-952cee410b6e" xlink:to="loc_gntx_OtherSegmentMember_32f879a9-01f4-4574-801e-40b53f95674e" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.gentex.com/role/Leases" xlink:type="simple" xlink:href="gntx-20200630.xsd#Leases"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/Leases" xlink:type="extended" id="i5a5a4b1a1a2a4920843bd7f9250d78b5_Leases"/>
  <link:roleRef roleURI="http://www.gentex.com/role/LeasesTables" xlink:type="simple" xlink:href="gntx-20200630.xsd#LeasesTables"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/LeasesTables" xlink:type="extended" id="i5f98378eac6b45dc82cfdb1d5401f4ab_LeasesTables"/>
  <link:roleRef roleURI="http://www.gentex.com/role/LeasesDetails" xlink:type="simple" xlink:href="gntx-20200630.xsd#LeasesDetails"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/LeasesDetails" xlink:type="extended" id="ic03519a39f2a46029c18879a9283d65f_LeasesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeLeaseDescriptionLineItems_3d96eee0-fe15-4ab5-a396-cb173fe59946" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeLeaseDescriptionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseRemainingLeaseTerm_635ddc84-7243-41f2-ba95-9c3ec1016786" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeOperatingLeaseRemainingLeaseTerm"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_3d96eee0-fe15-4ab5-a396-cb173fe59946" xlink:to="loc_us-gaap_LesseeOperatingLeaseRemainingLeaseTerm_635ddc84-7243-41f2-ba95-9c3ec1016786" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseWeightedAverageRemainingLeaseTerm1_0f9ddc22-ef6e-420f-9e62-5ad721efb901" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeaseWeightedAverageRemainingLeaseTerm1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_3d96eee0-fe15-4ab5-a396-cb173fe59946" xlink:to="loc_us-gaap_OperatingLeaseWeightedAverageRemainingLeaseTerm1_0f9ddc22-ef6e-420f-9e62-5ad721efb901" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseWeightedAverageDiscountRatePercent_bcb93474-16bc-4523-840a-c858b259c1ab" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeaseWeightedAverageDiscountRatePercent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_3d96eee0-fe15-4ab5-a396-cb173fe59946" xlink:to="loc_us-gaap_OperatingLeaseWeightedAverageDiscountRatePercent_bcb93474-16bc-4523-840a-c858b259c1ab" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsRemainderOfFiscalYear_ca543f4f-90fe-4475-a4b0-94eae4c476b8" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsRemainderOfFiscalYear"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_3d96eee0-fe15-4ab5-a396-cb173fe59946" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsRemainderOfFiscalYear_ca543f4f-90fe-4475-a4b0-94eae4c476b8" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths_9ac13ff4-ccd5-41b6-9503-0bc16a8b9ade" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_3d96eee0-fe15-4ab5-a396-cb173fe59946" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths_9ac13ff4-ccd5-41b6-9503-0bc16a8b9ade" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearTwo_1f151b9d-cf7a-4b7c-b328-595ff73d7e59" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearTwo"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_3d96eee0-fe15-4ab5-a396-cb173fe59946" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearTwo_1f151b9d-cf7a-4b7c-b328-595ff73d7e59" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearThree_8c67fb68-be6e-49d2-b9a8-d4236f5120cd" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearThree"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_3d96eee0-fe15-4ab5-a396-cb173fe59946" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearThree_8c67fb68-be6e-49d2-b9a8-d4236f5120cd" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFour_e17a3f57-c13b-452a-acd5-65d8e5c58dc4" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFour"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_3d96eee0-fe15-4ab5-a396-cb173fe59946" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFour_e17a3f57-c13b-452a-acd5-65d8e5c58dc4" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_LesseeOperatingLeaseLiabilityToBePaidDueAfterYearFour_d494b1af-8a75-4f9e-acb9-c79e7bff9ab0" xlink:href="gntx-20200630.xsd#gntx_LesseeOperatingLeaseLiabilityToBePaidDueAfterYearFour"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_3d96eee0-fe15-4ab5-a396-cb173fe59946" xlink:to="loc_gntx_LesseeOperatingLeaseLiabilityToBePaidDueAfterYearFour_d494b1af-8a75-4f9e-acb9-c79e7bff9ab0" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_62fc51fe-2dc9-4c58-8548-23b0f8fa34c0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_3d96eee0-fe15-4ab5-a396-cb173fe59946" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_62fc51fe-2dc9-4c58-8548-23b0f8fa34c0" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount_cc62e8bd-f2c4-4446-a7f8-125eb7e019b0" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_3d96eee0-fe15-4ab5-a396-cb173fe59946" xlink:to="loc_us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount_cc62e8bd-f2c4-4446-a7f8-125eb7e019b0" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiability_a45aa446-2b2a-40d5-9b72-288d6875babd" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeaseLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_3d96eee0-fe15-4ab5-a396-cb173fe59946" xlink:to="loc_us-gaap_OperatingLeaseLiability_a45aa446-2b2a-40d5-9b72-288d6875babd" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiabilityCurrent_030e7045-f831-4a51-b5e4-8d497711774c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeaseLiabilityCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_3d96eee0-fe15-4ab5-a396-cb173fe59946" xlink:to="loc_us-gaap_OperatingLeaseLiabilityCurrent_030e7045-f831-4a51-b5e4-8d497711774c" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiabilityNoncurrent_00c6928f-641d-4d55-80fc-5d7e8a07d4d2" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeaseLiabilityNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_3d96eee0-fe15-4ab5-a396-cb173fe59946" xlink:to="loc_us-gaap_OperatingLeaseLiabilityNoncurrent_00c6928f-641d-4d55-80fc-5d7e8a07d4d2" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseLiability_b4f26263-4b73-4370-8fe7-b39868cf3018" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_OperatingLeaseLiability"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeLeaseDescriptionTable_9b7a5af9-515e-4e88-99ea-7f9277f4567d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_LesseeLeaseDescriptionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_3d96eee0-fe15-4ab5-a396-cb173fe59946" xlink:to="loc_us-gaap_LesseeLeaseDescriptionTable_9b7a5af9-515e-4e88-99ea-7f9277f4567d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_09cafa77-3ad9-4a37-a31f-8d59276a041d" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LesseeLeaseDescriptionTable_9b7a5af9-515e-4e88-99ea-7f9277f4567d" xlink:to="loc_srt_RangeAxis_09cafa77-3ad9-4a37-a31f-8d59276a041d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_09cafa77-3ad9-4a37-a31f-8d59276a041d_default" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_09cafa77-3ad9-4a37-a31f-8d59276a041d" xlink:to="loc_srt_RangeMember_09cafa77-3ad9-4a37-a31f-8d59276a041d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_4162c019-c08f-47b9-bccb-9b87d4109027" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_09cafa77-3ad9-4a37-a31f-8d59276a041d" xlink:to="loc_srt_RangeMember_4162c019-c08f-47b9-bccb-9b87d4109027" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_fd1bdd56-50da-4865-9381-17e7806eca9e" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_4162c019-c08f-47b9-bccb-9b87d4109027" xlink:to="loc_srt_MinimumMember_fd1bdd56-50da-4865-9381-17e7806eca9e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_cabceeb1-b20b-4435-a533-9ca4e398285a" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_4162c019-c08f-47b9-bccb-9b87d4109027" xlink:to="loc_srt_MaximumMember_cabceeb1-b20b-4435-a533-9ca4e398285a" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.gentex.com/role/AcquisitionofVaporsensInc" xlink:type="simple" xlink:href="gntx-20200630.xsd#AcquisitionofVaporsensInc"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/AcquisitionofVaporsensInc" xlink:type="extended" id="ic6303b1f96df48f99b9a8c1c192633ad_AcquisitionofVaporsensInc"/>
  <link:roleRef roleURI="http://www.gentex.com/role/AcquisitionofVaporsensIncTables" xlink:type="simple" xlink:href="gntx-20200630.xsd#AcquisitionofVaporsensIncTables"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/AcquisitionofVaporsensIncTables" xlink:type="extended" id="i227846712e5e436b947c30919af03b75_AcquisitionofVaporsensIncTables"/>
  <link:roleRef roleURI="http://www.gentex.com/role/AcquisitionofVaporsensIncDetails" xlink:type="simple" xlink:href="gntx-20200630.xsd#AcquisitionofVaporsensIncDetails"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/AcquisitionofVaporsensIncDetails" xlink:type="extended" id="i5402917327d84ac285e5d082c32ac505_AcquisitionofVaporsensIncDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionLineItems_81fc85e1-4a50-49cd-a5b8-82ace5cc8b2d" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationConsiderationTransferred1_ee4df7c7-b18c-4492-bd90-392a2a9af07c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationConsiderationTransferred1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_81fc85e1-4a50-49cd-a5b8-82ace5cc8b2d" xlink:to="loc_us-gaap_BusinessCombinationConsiderationTransferred1_ee4df7c7-b18c-4492-bd90-392a2a9af07c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestments_5f7e7912-85e5-4dd8-b2f6-e48a7d937cb8" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquityMethodInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_81fc85e1-4a50-49cd-a5b8-82ace5cc8b2d" xlink:to="loc_us-gaap_EquityMethodInvestments_5f7e7912-85e5-4dd8-b2f6-e48a7d937cb8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireBusinessesGross_abf0937a-197a-4e59-8edb-6b4b7934667c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_PaymentsToAcquireBusinessesGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_81fc85e1-4a50-49cd-a5b8-82ace5cc8b2d" xlink:to="loc_us-gaap_PaymentsToAcquireBusinessesGross_abf0937a-197a-4e59-8edb-6b4b7934667c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionEquityInterestIssuedOrIssuableValueAssigned_8184bdf8-c052-46bd-8bfd-96489b5bcea8" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionEquityInterestIssuedOrIssuableValueAssigned"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_81fc85e1-4a50-49cd-a5b8-82ace5cc8b2d" xlink:to="loc_us-gaap_BusinessAcquisitionEquityInterestIssuedOrIssuableValueAssigned_8184bdf8-c052-46bd-8bfd-96489b5bcea8" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired_4afe7e20-377f-4f22-ac4f-93acf991d45c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_81fc85e1-4a50-49cd-a5b8-82ace5cc8b2d" xlink:to="loc_us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired_4afe7e20-377f-4f22-ac4f-93acf991d45c" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionCostOfAcquiredEntityTransactionCosts_fd90e8a2-734d-4495-bca0-e08b861a5d27" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionCostOfAcquiredEntityTransactionCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_81fc85e1-4a50-49cd-a5b8-82ace5cc8b2d" xlink:to="loc_us-gaap_BusinessAcquisitionCostOfAcquiredEntityTransactionCosts_fd90e8a2-734d-4495-bca0-e08b861a5d27" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_bdf2ccc1-b2fd-40ef-a412-a407f12bb84b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_81fc85e1-4a50-49cd-a5b8-82ace5cc8b2d" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_bdf2ccc1-b2fd-40ef-a412-a407f12bb84b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_31cc1c66-2fab-48e5-8181-ebc37f8fdf97" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_bdf2ccc1-b2fd-40ef-a412-a407f12bb84b" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_31cc1c66-2fab-48e5-8181-ebc37f8fdf97" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_31cc1c66-2fab-48e5-8181-ebc37f8fdf97_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_31cc1c66-2fab-48e5-8181-ebc37f8fdf97" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_31cc1c66-2fab-48e5-8181-ebc37f8fdf97_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_a9224de3-4d40-405e-8c38-fc5c46043352" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_31cc1c66-2fab-48e5-8181-ebc37f8fdf97" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_a9224de3-4d40-405e-8c38-fc5c46043352" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_VaporsensIncMember_a5e73c53-e3c5-4e18-8949-f6c717173be2" xlink:href="gntx-20200630.xsd#gntx_VaporsensIncMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_a9224de3-4d40-405e-8c38-fc5c46043352" xlink:to="loc_gntx_VaporsensIncMember_a5e73c53-e3c5-4e18-8949-f6c717173be2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityInterestIssuedOrIssuableByTypeAxis_5609b7fd-e3a3-4ab7-b7de-bbc10f8a481f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquityInterestIssuedOrIssuableByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_bdf2ccc1-b2fd-40ef-a412-a407f12bb84b" xlink:to="loc_us-gaap_EquityInterestIssuedOrIssuableByTypeAxis_5609b7fd-e3a3-4ab7-b7de-bbc10f8a481f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityInterestIssuedOrIssuableTypeDomain_5609b7fd-e3a3-4ab7-b7de-bbc10f8a481f_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquityInterestIssuedOrIssuableTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_EquityInterestIssuedOrIssuableByTypeAxis_5609b7fd-e3a3-4ab7-b7de-bbc10f8a481f" xlink:to="loc_us-gaap_EquityInterestIssuedOrIssuableTypeDomain_5609b7fd-e3a3-4ab7-b7de-bbc10f8a481f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityInterestIssuedOrIssuableTypeDomain_35ee246c-efee-4374-b825-a85a72886a98" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_EquityInterestIssuedOrIssuableTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_EquityInterestIssuedOrIssuableByTypeAxis_5609b7fd-e3a3-4ab7-b7de-bbc10f8a481f" xlink:to="loc_us-gaap_EquityInterestIssuedOrIssuableTypeDomain_35ee246c-efee-4374-b825-a85a72886a98" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_186e46c8-bece-4ff4-891e-6f9d0504c71e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityInterestIssuedOrIssuableTypeDomain_35ee246c-efee-4374-b825-a85a72886a98" xlink:to="loc_us-gaap_CommonStockMember_186e46c8-bece-4ff4-891e-6f9d0504c71e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementClassOfStockAxis_7226bf51-a380-4be1-9e46-3d8263c4a3b7" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_StatementClassOfStockAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_bdf2ccc1-b2fd-40ef-a412-a407f12bb84b" xlink:to="loc_us-gaap_StatementClassOfStockAxis_7226bf51-a380-4be1-9e46-3d8263c4a3b7" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_7226bf51-a380-4be1-9e46-3d8263c4a3b7_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementClassOfStockAxis_7226bf51-a380-4be1-9e46-3d8263c4a3b7" xlink:to="loc_us-gaap_ClassOfStockDomain_7226bf51-a380-4be1-9e46-3d8263c4a3b7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfStockDomain_8046131e-3eec-44ea-84d1-69cb593439fa" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_ClassOfStockDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementClassOfStockAxis_7226bf51-a380-4be1-9e46-3d8263c4a3b7" xlink:to="loc_us-gaap_ClassOfStockDomain_8046131e-3eec-44ea-84d1-69cb593439fa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockMember_acbb1350-9d3a-48df-95a8-d0ff1537bbec" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_RestrictedStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ClassOfStockDomain_8046131e-3eec-44ea-84d1-69cb593439fa" xlink:to="loc_us-gaap_RestrictedStockMember_acbb1350-9d3a-48df-95a8-d0ff1537bbec" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_4d572bf6-9cff-4925-99c8-c6cf7a49015c" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_bdf2ccc1-b2fd-40ef-a412-a407f12bb84b" xlink:to="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_4d572bf6-9cff-4925-99c8-c6cf7a49015c" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_4d572bf6-9cff-4925-99c8-c6cf7a49015c_default" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_4d572bf6-9cff-4925-99c8-c6cf7a49015c" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_4d572bf6-9cff-4925-99c8-c6cf7a49015c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_44d7c834-bb8b-45aa-a19d-982d91ef9de0" xlink:href="http://xbrl.fasb.org/srt/2020/elts/srt-2020-01-31.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_4d572bf6-9cff-4925-99c8-c6cf7a49015c" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_44d7c834-bb8b-45aa-a19d-982d91ef9de0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_VaporsensIncMember_dc210c37-6be8-4223-9f34-a3fc4f0e300f" xlink:href="gntx-20200630.xsd#gntx_VaporsensIncMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_44d7c834-bb8b-45aa-a19d-982d91ef9de0" xlink:to="loc_gntx_VaporsensIncMember_dc210c37-6be8-4223-9f34-a3fc4f0e300f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_eddda8a4-2f5d-47da-a59e-5e01670fcb47" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeStatementLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_bdf2ccc1-b2fd-40ef-a412-a407f12bb84b" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_eddda8a4-2f5d-47da-a59e-5e01670fcb47" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_eddda8a4-2f5d-47da-a59e-5e01670fcb47_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_eddda8a4-2f5d-47da-a59e-5e01670fcb47" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_eddda8a4-2f5d-47da-a59e-5e01670fcb47_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_40e70bbe-0e7c-46c6-beb3-e6dd3dc8807f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_eddda8a4-2f5d-47da-a59e-5e01670fcb47" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_40e70bbe-0e7c-46c6-beb3-e6dd3dc8807f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SellingGeneralAndAdministrativeExpensesMember_4fe5b5d0-264e-4b00-bcbe-ea39cf774d5c" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_SellingGeneralAndAdministrativeExpensesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_40e70bbe-0e7c-46c6-beb3-e6dd3dc8807f" xlink:to="loc_us-gaap_SellingGeneralAndAdministrativeExpensesMember_4fe5b5d0-264e-4b00-bcbe-ea39cf774d5c" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.gentex.com/role/AcquisitionofVaporsensIncScheduleofAssetsAcquiredandLiabilitiesAssumedDetails" xlink:type="simple" xlink:href="gntx-20200630.xsd#AcquisitionofVaporsensIncScheduleofAssetsAcquiredandLiabilitiesAssumedDetails"/>
  <link:definitionLink xlink:role="http://www.gentex.com/role/AcquisitionofVaporsensIncScheduleofAssetsAcquiredandLiabilitiesAssumedDetails" xlink:type="extended" id="i931fa1647f5141a1be90c51a413aefc8_AcquisitionofVaporsensIncScheduleofAssetsAcquiredandLiabilitiesAssumedDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_2a865c88-c83d-4c81-b87a-07f7d57ffab7" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssets_3dc8944c-f3b1-4d7a-a6df-f841d59b3597" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_2a865c88-c83d-4c81-b87a-07f7d57ffab7" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssets_3dc8944c-f3b1-4d7a-a6df-f841d59b3597" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedEquipment_7900f5b4-61df-4315-a6d8-be4deb097b80" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedEquipment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_2a865c88-c83d-4c81-b87a-07f7d57ffab7" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedEquipment_7900f5b4-61df-4315-a6d8-be4deb097b80" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles_c69b25b1-eabd-4295-a5df-1fce0d527ca3" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_2a865c88-c83d-4c81-b87a-07f7d57ffab7" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles_c69b25b1-eabd-4295-a5df-1fce0d527ca3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_ca586321-fd93-4772-967d-cca56db72095" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_Goodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_2a865c88-c83d-4c81-b87a-07f7d57ffab7" xlink:to="loc_us-gaap_Goodwill_ca586321-fd93-4772-967d-cca56db72095" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets_70fe67f7-dfa2-437a-a5a7-7a2842f1696f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_2a865c88-c83d-4c81-b87a-07f7d57ffab7" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedAssets_70fe67f7-dfa2-437a-a5a7-7a2842f1696f" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilities_21ff4fda-b358-470d-961e-404976eeac0b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_2a865c88-c83d-4c81-b87a-07f7d57ffab7" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilities_21ff4fda-b358-470d-961e-404976eeac0b" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeferredTaxLiabilities_dbeee7a5-ced5-434a-8fd1-cdaf71e35cf5" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeferredTaxLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_2a865c88-c83d-4c81-b87a-07f7d57ffab7" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeferredTaxLiabilities_dbeee7a5-ced5-434a-8fd1-cdaf71e35cf5" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities_136694f5-16bd-4a10-897b-1475b583aa4f" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_2a865c88-c83d-4c81-b87a-07f7d57ffab7" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedLiabilities_136694f5-16bd-4a10-897b-1475b583aa4f" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet_487986be-7676-4959-9c0e-a2d23fd51f31" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_2a865c88-c83d-4c81-b87a-07f7d57ffab7" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredGoodwillAndLiabilitiesAssumedNet_487986be-7676-4959-9c0e-a2d23fd51f31" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAcquiredAsPartOfBusinessCombinationTable_19f8ff9c-2a7a-402c-9efc-9b860efad2ea" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAcquiredAsPartOfBusinessCombinationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_2a865c88-c83d-4c81-b87a-07f7d57ffab7" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAcquiredAsPartOfBusinessCombinationTable_19f8ff9c-2a7a-402c-9efc-9b860efad2ea" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_84e3d66e-3465-4a91-b46d-770da5510b0b" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsAcquiredAsPartOfBusinessCombinationTable_19f8ff9c-2a7a-402c-9efc-9b860efad2ea" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_84e3d66e-3465-4a91-b46d-770da5510b0b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_84e3d66e-3465-4a91-b46d-770da5510b0b_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_84e3d66e-3465-4a91-b46d-770da5510b0b" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_84e3d66e-3465-4a91-b46d-770da5510b0b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_c77afbc8-5b4e-4368-a360-9a58c028b726" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_84e3d66e-3465-4a91-b46d-770da5510b0b" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_c77afbc8-5b4e-4368-a360-9a58c028b726" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TechnologyBasedIntangibleAssetsMember_d087e2e4-844a-4c63-9e92-a7289ae2d60e" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_TechnologyBasedIntangibleAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_c77afbc8-5b4e-4368-a360-9a58c028b726" xlink:to="loc_us-gaap_TechnologyBasedIntangibleAssetsMember_d087e2e4-844a-4c63-9e92-a7289ae2d60e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InProcessResearchAndDevelopmentMember_e553a999-62a7-45dd-9654-7cda5b9a49af" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_InProcessResearchAndDevelopmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_c77afbc8-5b4e-4368-a360-9a58c028b726" xlink:to="loc_us-gaap_InProcessResearchAndDevelopmentMember_e553a999-62a7-45dd-9654-7cda5b9a49af" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_6040e966-33bb-4ff8-adc3-88c1e9e5a2df" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsAcquiredAsPartOfBusinessCombinationTable_19f8ff9c-2a7a-402c-9efc-9b860efad2ea" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_6040e966-33bb-4ff8-adc3-88c1e9e5a2df" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_6040e966-33bb-4ff8-adc3-88c1e9e5a2df_default" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_6040e966-33bb-4ff8-adc3-88c1e9e5a2df" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_6040e966-33bb-4ff8-adc3-88c1e9e5a2df_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_8241f99f-2241-4e59-97a5-9b0cb1a66a64" xlink:href="http://xbrl.fasb.org/us-gaap/2020/elts/us-gaap-2020-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_6040e966-33bb-4ff8-adc3-88c1e9e5a2df" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_8241f99f-2241-4e59-97a5-9b0cb1a66a64" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_gntx_VaporsensIncMember_92eb56c5-62db-4132-868c-4934e1e3060e" xlink:href="gntx-20200630.xsd#gntx_VaporsensIncMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_8241f99f-2241-4e59-97a5-9b0cb1a66a64" xlink:to="loc_gntx_VaporsensIncMember_92eb56c5-62db-4132-868c-4934e1e3060e" xlink:type="arc" order="0"/>
  </link:definitionLink>
</link:linkbase>
